Re: [R] the less-than-minus gotcha
Steve (and any others still paying attention to this thread), Larry Wall (author of Perl) said something along the lines of: things that are similar should look similar, things that are different should look different. Ironically one of the first places I saw that quote was in a Perl vs. Python language war and the same quote was being used by both sides. This made me think that you can learn a lot about how programmers think by what they make look similar and what they make look different (and therefore what they think are similar and different). In R, I see the assignments: foo( x <- something ) as assign to the variable x in the current (or calling) environment and foo( x = something ) as assign to the variable x in the environment created by the function call. With this distinction only "<-" makes any sense at the top level, but then I see assigning to the 2 different environments as 2 different things that should look different. Using "=" for assignment makes sense if (and only if) you consider assigning into different environments to be the same (or at least very similar) thing. Also you mentioned that foo( x <- something ) should always be written as: x <- something foo(x) and for many cases I agree, but consider the counter example of: system.time( out <- longRunningSimulationFunction(n=1e6) ) compared to: out = longRunningSimulationFunction(n=1e6) system.time(out) I would argue that the 1st version is much more useful than the 2nd. On Mon, Feb 2, 2015 at 6:57 PM, Steve Taylor wrote: > Responding to several messages in this thread... > > > > All the more reason to use = instead of <- > > Definitely not! > > Martin and Rolf are right, it's not a reason for that; I wrote that > quickly without thinking it through. An "=" user might be more likely to > fall for the gotcha, if not spacing their code nicely. So the lesson > learned from the gotcha is that it's good to space your code nicely, as > others have siad, not which assignment symbol to use. > > However, I continue to use "=" for assignment on a daily basis without any > problems, as I have done for many years. I remain unconvinced by any and > all of these arguments against it in favour of "<-". People telling me > that I "should" use the arrow need better agruments than what I've seen so > far. > > I find "<-" ugly and "->" useless/pointless, whereas "=" is simpler and > also nicely familiar from my experience in other languages. It doesn't > matter to me that "=" is not commutative because I don't need it to be. > > > Further it can be nicely marked up by a real "left arrow" > > by e.g. the listings LaTeX 'listings' package... > > Now that's just silly, turning R code into graphical characters that are > not part of the R language. > > > foo(x = y) and foo(x <- y) > > I'm well aware of this distinction and it never causes me any problems. > The latter is an example of bad (obfuscated) coding, IMHO; it should be > done in two lines for clarity as follows: > > x = y > foo(x) > > > Using = has it's problems too. > Same goes for apostrophes. > > Shall we discuss putting "else" at the start of line next? > > cheers, > Steve > > __ > R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide > http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. > -- Gregory (Greg) L. Snow Ph.D. 538...@gmail.com [[alternative HTML version deleted]] __ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
Re: [R] the less-than-minus gotcha
>>>>> Steve Taylor
>>>>> on Tue, 3 Feb 2015 03:11:47 + writes:
> Nobody would write x=x or indeed x<-x; both are silly. If
> I found myself writing f(x=x) I might smirk at the
> coincidence, but it wouldn't bother me. I certainly
> wouldn't confuse it with assigning x to itself. By the
> way, here's another assignment operator we can use:
> `:=` = `<-` # this is going in my .Rprofile
> x := 1
I very much agree with you on that last point.
A while ago, about or shortly before when R was created, say ca. 1991-1993,
when S4 was "around the corner", and I was a beta tester for it,
and '=' was going to be introduced into the S language,
I had a fervent plea for considering ":=" as an alternative...
... but was never even replied to IIRC.
The fact that R's parser allows ':=' is an interesting
historic relict itself.
Before R even got a version number, R did not have packages yet,
there was "kind of a distinction" (don't ask me for details now)
between "base R functions" and "other R objects"
{If Ross Ihaka reads this, he will cringe I'm sure.. sorry, Ross!}
and all those used :=
The last version that still used this extensively 0.13, is still available
as R-0.13alpha.tar.gz (813570 bytes, dated Nov 7, 1996),
and contains a file src/library/base/median (note, no 'R'
subdirectory) which looks like this
-
median := function(x, na.rm = FALSE) {
if(na.rm)
x <- x[!is.na(x)]
else if(any(is.na(x)))
return(NA)
n <- length(x)
half <- (n + 1)/2
if(n %% 2 == 1) {
sort(x, partial = half)[half]
}
else {
sum(sort(x, partial = c(half, half + 1))[c(half, half + 1)])/2
}
}
-
so yes, ":=" had its nice history, but as it was not accepted
into S *instead* of '=', it also fell away for R ...
Martin Maechler,
ETH Zurich (and R Core team since "prehistory")
> -----Original Message- From: Jeff Newmiller
> [mailto:jdnew...@dcn.davis.ca.us] Sent: Tuesday, 3
> February 2015 3:54p To: Steve Taylor;
> r-h...@stat.math.ethz.ch Subject: Re: [R] the
> less-than-minus gotcha
> I did not start out liking <-, but I am quite attached to
> it now, and even Rcpp feels weird to me now. This may seem
> like yet another variation on a theme that you don't find
> compelling, but I find that
> f(x=x)
> makes sense when scope is considered, but
> x=x
> on its own is silly. That is why I prefer to reserve = for
> assigning parameters... I use it to clarify that I am
> crossing scope boundaries, while <- never does. (<<- is a
> dangerous animal, though... to be used only locally in
> nested function definitions).
> In my view, this is similar to preferring == from
> C-derived syntaxes over the overloaded = from, say,
> Basic. I am sure you can get by with the syntactic
> overloading, but if you have the option of reducing
> ambiguity, why not use it?
>
---
> Jeff Newmiller The . . Go Live...
> DCN: Basics: ##.#. ##.#. Live
> Go... Live: OO#.. Dead: OO#.. Playing Research Engineer
> (Solar/Batteries O.O#. #.O#. with /Software/Embedded
> Controllers) .OO#. .OO#. rocks...1k
>
---
> Sent from my phone. Please excuse my brevity.
> On February 2, 2015 5:57:05 PM PST, Steve Taylor
> wrote:
>> Responding to several messages in this thread...
>>
>>> > All the more reason to use = instead of <- Definitely
>>> not!
>>
>> Martin and Rolf are right, it's not a reason for that; I
>> wrote that quickly without thinking it through. An "="
>> user might be more likely to fall for the gotcha, if not
>> spacing their code nicely. So the lesson learned from
>> the gotcha is that it's good to space your code nicely,
>> as others have siad, not which assignment symbol to use.
>>
>> However, I continue to use "=" for assignment on a daily
>> basis without any problems, as I have done for many
>> years. I remain unconvinced by any and all of these
>> arguments against it in favour of "<-". People telling
&g
Re: [R] the less-than-minus gotcha
Kevin Thorpe wrote, "Moral of story, computers do what you tell them, not what you meant." But hope springs eternal! Of course this aphorism explains neatly every problem I've ever run across while using a computer. But maybe someday they'll make a computer that undertands *me*! Peter Dalgaard wrote, "I'd rather say that it is good reason to use spaces around operators. Makes the code easier to read too." I think that's the real lesson. I try to do that, but I'll be trying even harder now. If they'd thought of it long ago, S and R could have been written so that "<-" had to be followed by a space or an error would result. That might have been a good idea, but it's too late now. So we just have to not make mistakes. I'm working on it. Mike __ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
Re: [R] the less-than-minus gotcha
Nobody would write x=x or indeed x<-x; both are silly. If I found myself writing f(x=x) I might smirk at the coincidence, but it wouldn't bother me. I certainly wouldn't confuse it with assigning x to itself. By the way, here's another assignment operator we can use: `:=` = `<-` # this is going in my .Rprofile x := 1 -Original Message- From: Jeff Newmiller [mailto:jdnew...@dcn.davis.ca.us] Sent: Tuesday, 3 February 2015 3:54p To: Steve Taylor; r-h...@stat.math.ethz.ch Subject: Re: [R] the less-than-minus gotcha I did not start out liking <-, but I am quite attached to it now, and even Rcpp feels weird to me now. This may seem like yet another variation on a theme that you don't find compelling, but I find that f(x=x) makes sense when scope is considered, but x=x on its own is silly. That is why I prefer to reserve = for assigning parameters... I use it to clarify that I am crossing scope boundaries, while <- never does. (<<- is a dangerous animal, though... to be used only locally in nested function definitions). In my view, this is similar to preferring == from C-derived syntaxes over the overloaded = from, say, Basic. I am sure you can get by with the syntactic overloading, but if you have the option of reducing ambiguity, why not use it? --- Jeff NewmillerThe . . Go Live... DCN:Basics: ##.#. ##.#. Live Go... Live: OO#.. Dead: OO#.. Playing Research Engineer (Solar/BatteriesO.O#. #.O#. with /Software/Embedded Controllers) .OO#. .OO#. rocks...1k --- Sent from my phone. Please excuse my brevity. On February 2, 2015 5:57:05 PM PST, Steve Taylor wrote: >Responding to several messages in this thread... > >> > All the more reason to use = instead of <- >> Definitely not! > >Martin and Rolf are right, it's not a reason for that; I wrote that >quickly without thinking it through. An "=" user might be more likely >to fall for the gotcha, if not spacing their code nicely. So the >lesson learned from the gotcha is that it's good to space your code >nicely, as others have siad, not which assignment symbol to use. > >However, I continue to use "=" for assignment on a daily basis without >any problems, as I have done for many years. I remain unconvinced by >any and all of these arguments against it in favour of "<-". People >telling me that I "should" use the arrow need better agruments than >what I've seen so far. > >I find "<-" ugly and "->" useless/pointless, whereas "=" is simpler and >also nicely familiar from my experience in other languages. It doesn't >matter to me that "=" is not commutative because I don't need it to be. > >> Further it can be nicely marked up by a real "left arrow" >> by e.g. the listings LaTeX 'listings' package... > >Now that's just silly, turning R code into graphical characters that >are not part of the R language. > >> foo(x = y) and foo(x <- y) > >I'm well aware of this distinction and it never causes me any problems. >The latter is an example of bad (obfuscated) coding, IMHO; it should be >done in two lines for clarity as follows: > >x = y >foo(x) > >> Using = has it's problems too. >Same goes for apostrophes. > >Shall we discuss putting "else" at the start of line next? > >cheers, > Steve > >__ >R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see >https://stat.ethz.ch/mailman/listinfo/r-help >PLEASE do read the posting guide >http://www.R-project.org/posting-guide.html >and provide commented, minimal, self-contained, reproducible code. __ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
Re: [R] the less-than-minus gotcha
I did not start out liking <-, but I am quite attached to it now, and even Rcpp feels weird to me now. This may seem like yet another variation on a theme that you don't find compelling, but I find that f(x=x) makes sense when scope is considered, but x=x on its own is silly. That is why I prefer to reserve = for assigning parameters... I use it to clarify that I am crossing scope boundaries, while <- never does. (<<- is a dangerous animal, though... to be used only locally in nested function definitions). In my view, this is similar to preferring == from C-derived syntaxes over the overloaded = from, say, Basic. I am sure you can get by with the syntactic overloading, but if you have the option of reducing ambiguity, why not use it? --- Jeff NewmillerThe . . Go Live... DCN:Basics: ##.#. ##.#. Live Go... Live: OO#.. Dead: OO#.. Playing Research Engineer (Solar/BatteriesO.O#. #.O#. with /Software/Embedded Controllers) .OO#. .OO#. rocks...1k --- Sent from my phone. Please excuse my brevity. On February 2, 2015 5:57:05 PM PST, Steve Taylor wrote: >Responding to several messages in this thread... > >> > All the more reason to use = instead of <- >> Definitely not! > >Martin and Rolf are right, it's not a reason for that; I wrote that >quickly without thinking it through. An "=" user might be more likely >to fall for the gotcha, if not spacing their code nicely. So the >lesson learned from the gotcha is that it's good to space your code >nicely, as others have siad, not which assignment symbol to use. > >However, I continue to use "=" for assignment on a daily basis without >any problems, as I have done for many years. I remain unconvinced by >any and all of these arguments against it in favour of "<-". People >telling me that I "should" use the arrow need better agruments than >what I've seen so far. > >I find "<-" ugly and "->" useless/pointless, whereas "=" is simpler and >also nicely familiar from my experience in other languages. It doesn't >matter to me that "=" is not commutative because I don't need it to be. > >> Further it can be nicely marked up by a real "left arrow" >> by e.g. the listings LaTeX 'listings' package... > >Now that's just silly, turning R code into graphical characters that >are not part of the R language. > >> foo(x = y) and foo(x <- y) > >I'm well aware of this distinction and it never causes me any problems. >The latter is an example of bad (obfuscated) coding, IMHO; it should be >done in two lines for clarity as follows: > >x = y >foo(x) > >> Using = has it's problems too. >Same goes for apostrophes. > >Shall we discuss putting "else" at the start of line next? > >cheers, > Steve > >__ >R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see >https://stat.ethz.ch/mailman/listinfo/r-help >PLEASE do read the posting guide >http://www.R-project.org/posting-guide.html >and provide commented, minimal, self-contained, reproducible code. __ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
Re: [R] the less-than-minus gotcha
I disagree. Assignments in my code are all lines that look like this: variable = expression They are easy to find and easy to read. -Original Message- From: Ista Zahn [mailto:istaz...@gmail.com] Sent: Tuesday, 3 February 2015 3:36p To: Steve Taylor Cc: r-h...@stat.math.ethz.ch Subject: Re: [R] the less-than-minus gotcha On Mon, Feb 2, 2015 at 8:57 PM, Steve Taylor wrote: Fair enough, but you skipped right past the most important one: it makes code easier to read. It's very nice to be able to visually scan through the code and easily see where assignment happens. __ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
Re: [R] the less-than-minus gotcha
On Mon, Feb 2, 2015 at 8:57 PM, Steve Taylor wrote:
> Responding to several messages in this thread...
>
>> > All the more reason to use = instead of <-
>> Definitely not!
>
> Martin and Rolf are right, it's not a reason for that; I wrote that quickly
> without thinking it through. An "=" user might be more likely to fall for
> the gotcha, if not spacing their code nicely. So the lesson learned from the
> gotcha is that it's good to space your code nicely, as others have siad, not
> which assignment symbol to use.
>
> However, I continue to use "=" for assignment on a daily basis without any
> problems, as I have done for many years. I remain unconvinced by any and all
> of these arguments against it in favour of "<-". People telling me that I
> "should" use the arrow need better agruments than what I've seen so far.
Fair enough, but you skipped right past the most important one: it
makes code easier to read. It's very nice to be able to visually scan
through the code and easily see where assignment happens.
>
> I find "<-" ugly and "->" useless/pointless,
I never used it either, until recently when I started using magrittr.
Maybe still pointless, but I find the form
> library(magrittr)
>
> "hello" %>%
+ paste("world,") %>%
+ paste("my name is") %>%
+ paste("Ista") -> hi
> hi
[1] "hello world, my name is Ista"
quite nice.
--Ista
whereas "=" is simpler and also nicely familiar from my experience in
other languages. It doesn't matter to me that "=" is not commutative
because I don't need it to be.
>
>> Further it can be nicely marked up by a real "left arrow"
>> by e.g. the listings LaTeX 'listings' package...
>
> Now that's just silly, turning R code into graphical characters that are not
> part of the R language.
>
>> foo(x = y) and foo(x <- y)
>
> I'm well aware of this distinction and it never causes me any problems. The
> latter is an example of bad (obfuscated) coding, IMHO; it should be done in
> two lines for clarity as follows:
>
> x = y
> foo(x)
>
>> Using = has it's problems too.
> Same goes for apostrophes.
>
> Shall we discuss putting "else" at the start of line next?
>
> cheers,
> Steve
>
> __
> R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
__
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
Re: [R] the less-than-minus gotcha
Responding to several messages in this thread... > > All the more reason to use = instead of <- > Definitely not! Martin and Rolf are right, it's not a reason for that; I wrote that quickly without thinking it through. An "=" user might be more likely to fall for the gotcha, if not spacing their code nicely. So the lesson learned from the gotcha is that it's good to space your code nicely, as others have siad, not which assignment symbol to use. However, I continue to use "=" for assignment on a daily basis without any problems, as I have done for many years. I remain unconvinced by any and all of these arguments against it in favour of "<-". People telling me that I "should" use the arrow need better agruments than what I've seen so far. I find "<-" ugly and "->" useless/pointless, whereas "=" is simpler and also nicely familiar from my experience in other languages. It doesn't matter to me that "=" is not commutative because I don't need it to be. > Further it can be nicely marked up by a real "left arrow" > by e.g. the listings LaTeX 'listings' package... Now that's just silly, turning R code into graphical characters that are not part of the R language. > foo(x = y) and foo(x <- y) I'm well aware of this distinction and it never causes me any problems. The latter is an example of bad (obfuscated) coding, IMHO; it should be done in two lines for clarity as follows: x = y foo(x) > Using = has it's problems too. Same goes for apostrophes. Shall we discuss putting "else" at the start of line next? cheers, Steve __ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
Re: [R] the less-than-minus gotcha
> All the more reason to use = instead of <-
Definitely not!
(As you were told, there are other drawbacks).
R does not have to look like C, it *is* different in many ways.
If you use a decent IDE for R, you get spaces around ' <- ' for
free: Both in ESS and in Rstudio, you can use "[Alt] -"
to produce the 4 characters ' <- '
{ [Alt] + "-") is called 'M--' in ESS / emacs which has even
more options for " <- " and is fully configurable in its key
bindings anyway. }
The '=' character has many uses in R and using ' <- '
for assignment makes the code "more expressive": It makes sense
to highlight the assignment op, but is a bit stupid to
highlight all "=" signs. Further it can be nicely marked up by
a real "left arrow" by e.g. the listings LaTeX
'listings' package, or the (oldish) 'a2ps' GNU software.
Further, assignment is not commutative, and hence,
there is a corresponding ` -> ` operator,
whereas the '=' is a commutative operator in mathematics, but
not when used as assignment op.
[ yes: "Flame war is on. I'll stop reading R-help for a while.."
;-) ;-) ]
> -Original Message-
> From: R-help [mailto:r-help-boun...@r-project.org] On Behalf Of Ben Bolker
> Sent: Monday, 2 February 2015 2:07p
> To: r-h...@stat.math.ethz.ch
> Subject: Re: [R] the less-than-minus gotcha
> Mike Miller gmail.com> writes:
> >
> > I've got to remember to use more spaces. Here's the basic problem:
> >
> > These are the same:
> >
> > v< 1
> > v<1
> >
> > But these are extremely different:
> >
> > v< -1
> > v<-1
> >
> This is indeed documented, in passing, in one of the pages you listed:
> http://tim-smith.us/arrgh/syntax.html
> Whitespace is meaningless, unless it isn't. Some parsing ambiguities
> are resolved by considering whitespace around operators. See and
> despair: x<-y (assignment) is parsed differently than x < -y (comparison)!
__
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
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Re: [R] the less-than-minus gotcha
Rolf Turner is right on the money about not mixing-up '=' and '<-' Though this 'gotcha' will always a threat while '<-' is the assignment operator. The old Algol60 syntax of ':=' was less error-prone, but I guess '<-' is too firmly bedded-in to ever change. Meanwhile, spaces around the assignment operator gives less error-prone and more readable code. cheers Bob Kinley _ -Original Message- From: R-help [mailto:r-help-boun...@r-project.org] On Behalf Of Rolf Turner Sent: 02 February 2015 11:58 To: Steve Taylor; r-h...@stat.math.ethz.ch Subject: Re: [R] the less-than-minus gotcha On 02/02/15 14:26, Steve Taylor wrote: > All the more reason to use = instead of <- Couldn't agree less, Steve. The "<-" should be used for assignment. The "=" sign should be reserved for handling function arguments in the "name=value" form. Doing anything else invites confusion and occasionally chaos. Lots of examples have been given in the past involving syntax of the form foo(x = y) and foo(x <- y). cheers, Rolf -- Rolf Turner Technical Editor ANZJS Department of Statistics University of Auckland Phone: +64-9-373-7599 ext. 88276 Home phone: +64-9-480-4619 __ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code. __ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
Re: [R] the less-than-minus gotcha
On 02-Feb-2015 11:58:10 Rolf Turner wrote: > > On 02/02/15 14:26, Steve Taylor wrote: > >> All the more reason to use = instead of <- > > Couldn't agree less, Steve. The "<-" should be used for assignment. The > "=" sign should be reserved for handling function arguments in the > "name=value" form. Doing anything else invites confusion and > occasionally chaos. > > Lots of examples have been given in the past involving syntax of the > form foo(x = y) and foo(x <- y). > > cheers, > Rolf > -- > Rolf Turner As well as agreering with Rolf, it should also be said that Steve's advice "All the more reason to use = instead of <-" is not applicable in this context, which was: which( frame$var>4 ) # no problem which( frame$var<-4 ) # huge problem: frame$var is destroyed There is no place for an "=" here! What does not seems to have been mentioned so far is that this kind of thing can be safely wrapped in parentheses: which( frame$var>4 )# no problem oper which( frame$var<(-4) ) # [again no problem] Personally, I'm prone to using parentheses if I have any feeling that a "gotcha" may be lurking -- not only in the distinction between "var<-4" and "var< -4", but also to be confident that, for instance, my intentions are not being over-ridden by operator precedence rules. Some people object to code "clutter" from parentheses that could be more simply replaced (e.g. "var< -4" instead of "var<(-4)"), but parentheses ensure that it's right and also make it clear when one reads it. Best wishes to all, Ted. - E-Mail: (Ted Harding) Date: 02-Feb-2015 Time: 12:43:51 This message was sent by XFMail __ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
Re: [R] the less-than-minus gotcha
I'd rather say that it is good reason to use spaces around operators. Makes the code easier to read too. (_Possible_ to read for some.) We've probably all done it. I did, once upon a time in S-Plus, on the results of a multi-day simulation study: > <>$statistic [1] -1.28 > sim <- sapply(1:1, <>$statistic) . . leave running . > mean(sim<-1.28) # get empirical p-value [1] 1.28 ??!?... Uh-oh. On 02 Feb 2015, at 02:26 , Steve Taylor wrote: > All the more reason to use = instead of <- > > -- Peter Dalgaard, Professor, Center for Statistics, Copenhagen Business School Solbjerg Plads 3, 2000 Frederiksberg, Denmark Phone: (+45)38153501 Email: pd@cbs.dk Priv: pda...@gmail.com __ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
Re: [R] the less-than-minus gotcha
On 02/02/15 14:26, Steve Taylor wrote: All the more reason to use = instead of <- Couldn't agree less, Steve. The "<-" should be used for assignment. The "=" sign should be reserved for handling function arguments in the "name=value" form. Doing anything else invites confusion and occasionally chaos. Lots of examples have been given in the past involving syntax of the form foo(x = y) and foo(x <- y). cheers, Rolf -- Rolf Turner Technical Editor ANZJS Department of Statistics University of Auckland Phone: +64-9-373-7599 ext. 88276 Home phone: +64-9-480-4619 __ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
Re: [R] the less-than-minus gotcha
"Moral of story, computers do what you tell them, not what you meant." Not only a fortune, but profound wisdom. Jim On Mon, Feb 2, 2015 at 12:38 PM, Kevin E. Thorpe wrote: > Using = has it's problems too. > > For example, > > print(fit <- lm(...)) > > Assigns the result of the lm call to fit and prints the results. This is > quite a useful trick actually. > > print(fit = lm(...)) > > Throws an error. > > Moral of story, computers do what you tell them, not what you meant. > > Kevin > > On 02/01/2015 08:26 PM, Steve Taylor wrote: >> >> All the more reason to use = instead of <- >> >> >> -Original Message- >> From: R-help [mailto:r-help-boun...@r-project.org] On Behalf Of Ben Bolker >> Sent: Monday, 2 February 2015 2:07p >> To: r-h...@stat.math.ethz.ch >> Subject: Re: [R] the less-than-minus gotcha >> >> Mike Miller gmail.com> writes: >> >>> >>> I've got to remember to use more spaces. Here's the basic problem: >>> >>> These are the same: >>> >>> v< 1 >>> v<1 >>> >>> But these are extremely different: >>> >>> v< -1 >>> v<-1 >>> >> >> This is indeed documented, in passing, in one of the pages you listed: >> >> http://tim-smith.us/arrgh/syntax.html >> >> Whitespace is meaningless, unless it isn't. Some parsing ambiguities >> are resolved by considering whitespace around operators. See and >> despair: x<-y (assignment) is parsed differently than x < -y (comparison)! >> > > > -- > Kevin E. Thorpe > Head of Biostatistics, Applied Health Research Centre (AHRC) > Li Ka Shing Knowledge Institute of St. Michael's > Assistant Professor, Dalla Lana School of Public Health > University of Toronto > email: kevin.tho...@utoronto.ca Tel: 416.864.5776 Fax: 416.864.3016 > > > __ > R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. __ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
Re: [R] the less-than-minus gotcha
Using = has it's problems too. For example, print(fit <- lm(...)) Assigns the result of the lm call to fit and prints the results. This is quite a useful trick actually. print(fit = lm(...)) Throws an error. Moral of story, computers do what you tell them, not what you meant. Kevin On 02/01/2015 08:26 PM, Steve Taylor wrote: All the more reason to use = instead of <- -Original Message- From: R-help [mailto:r-help-boun...@r-project.org] On Behalf Of Ben Bolker Sent: Monday, 2 February 2015 2:07p To: r-h...@stat.math.ethz.ch Subject: Re: [R] the less-than-minus gotcha Mike Miller gmail.com> writes: I've got to remember to use more spaces. Here's the basic problem: These are the same: v< 1 v<1 But these are extremely different: v< -1 v<-1 This is indeed documented, in passing, in one of the pages you listed: http://tim-smith.us/arrgh/syntax.html Whitespace is meaningless, unless it isn't. Some parsing ambiguities are resolved by considering whitespace around operators. See and despair: x<-y (assignment) is parsed differently than x < -y (comparison)! -- Kevin E. Thorpe Head of Biostatistics, Applied Health Research Centre (AHRC) Li Ka Shing Knowledge Institute of St. Michael's Assistant Professor, Dalla Lana School of Public Health University of Toronto email: kevin.tho...@utoronto.ca Tel: 416.864.5776 Fax: 416.864.3016 __ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
Re: [R] the less-than-minus gotcha
All the more reason to use = instead of <- -Original Message- From: R-help [mailto:r-help-boun...@r-project.org] On Behalf Of Ben Bolker Sent: Monday, 2 February 2015 2:07p To: r-h...@stat.math.ethz.ch Subject: Re: [R] the less-than-minus gotcha Mike Miller gmail.com> writes: > > I've got to remember to use more spaces. Here's the basic problem: > > These are the same: > > v< 1 > v<1 > > But these are extremely different: > > v< -1 > v<-1 > This is indeed documented, in passing, in one of the pages you listed: http://tim-smith.us/arrgh/syntax.html Whitespace is meaningless, unless it isn't. Some parsing ambiguities are resolved by considering whitespace around operators. See and despair: x<-y (assignment) is parsed differently than x < -y (comparison)! __ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code. __ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
Re: [R] the less-than-minus gotcha
Mike Miller gmail.com> writes: > > I've got to remember to use more spaces. Here's the basic problem: > > These are the same: > > v< 1 > v<1 > > But these are extremely different: > > v< -1 > v<-1 > This is indeed documented, in passing, in one of the pages you listed: http://tim-smith.us/arrgh/syntax.html Whitespace is meaningless, unless it isn't. Some parsing ambiguities are resolved by considering whitespace around operators. See and despair: x<-y (assignment) is parsed differently than x < -y (comparison)! __ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
[R] the less-than-minus gotcha
I've got to remember to use more spaces. Here's the basic problem: These are the same: v< 1 v<1 But these are extremely different: v< -1 v<-1 This mistake can get you even inside of a function call like this: v <- -2:2 which( v<1 ) [1] 1 2 3 which( v<-1 ) # oops, I meant v< -1 not v<-1 a HUGE mistake! Error in which(v <- 1) : argument to 'which' is not logical v [1] 1 It throws an error but not because I just destroyed my data. R has no way of knowing that I didn't intend to overwrite the vector. This was how it got me: which( frame$var>4 ) # no problem which( frame$var<-4 ) # huge problem: frame$var is destroyed Too late now: The data in frame$var were all overwritten with 4s. So the data are lost and might not be recoverable. Maybe the tactic that will save me in the future is to remember to always use plenty of spaces: which( frame$var > 4 ) which( frame$var < -4 ) That also makes the code easier to read. In a script, I probably would have done that, but in an interactive session I can be lazy. It seems that there are a lot of "R gotcha" pages on the web but quite a few of the examples show R behaving exactly like I would want and expect (e.g., of course NA + 5 returns NA)... https://github.com/mikelove/r-gotchas/blob/master/README.md http://stackoverflow.com/questions/1535021/whats-the-biggest-r-gotcha-youve-run-across http://www.burns-stat.com/pages/Tutor/R_inferno.pdf http://biostat.mc.vanderbilt.edu/wiki/Main/LinuxWorkshopRProgramingTipsAndGotchas http://tim-smith.us/arrgh/ I didn't happen to see my example on any list, but I didn't read them thoroughly, so it's probably there. Mike __ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
