Re: [R] A More efficient method?
One other thing, in a multiprocessor configuration, if your application is
making use of the additional CPUs, then
User + System > Elapsed
In some cases.
On 7/4/07, jim holtman <[EMAIL PROTECTED]> wrote:
>
> User and System are a measure of the CPU time that was consumed. Elapsed
> time is the "wall clock" and even though they are both measured in seconds,
> they are not really the same units. The reason for the difference is any
> "idle" time that they system may have waiting for I/O to complete which does
> not consume CPU time for your process, but does consume Elasped time.
>
> For some instances of CPU intensive code (with no I/O of competing tasks),
> the User + System ~= Elapsed. Also you have to take into account the
> granularity of the clock when looking at numbers like 0.04. So serious
> comparisons of timing, you want runs of at least 10s of seconds or more.
>
>
> On 7/4/07, Stefan Grosse <[EMAIL PROTECTED]> wrote:
> >
> > Gabor Grothendieck wrote:
> > >> set.seed(1)
> > >> C <- sample(c("a", "b"), 10, replace = TRUE)
> > >> system.time(s1 <- ifelse(C == "a", 1, -1))
> > >>
> > >user system elapsed
> > >0.370.010.38
> > >
> > >> system.time(s2 <- 2 * (C == "a") - 1)
> > >>
> > >user system elapsed
> > >0.020.000.02
> > >
> > > system.time(s1 <- ifelse(C == "a", 1, -1))
> > user system elapsed
> > 0.040.010.08
> > > system.time(s2 <- 2 * (C == "a") - 1)
> > user system elapsed
> > 0 0 0
> >
> >
> > I am just wondering: how comes the time does add up to 0.05 while
> > elapsed states 0.08 on my system? (Vista+R2.5.1)
> >
> > Stefan
> >
> >
> > -=-=-
> > ... Time is an illusion, lunchtime doubly so. (Ford Prefect)
> >
> > __
> > R-help@stat.math.ethz.ch mailing list
> > 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.
> >
>
>
>
> --
> Jim Holtman
> Cincinnati, OH
> +1 513 646 9390
>
> What is the problem you are trying to solve?
--
Jim Holtman
Cincinnati, OH
+1 513 646 9390
What is the problem you are trying to solve?
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Re: [R] A More efficient method?
User and System are a measure of the CPU time that was consumed. Elapsed
time is the "wall clock" and even though they are both measured in seconds,
they are not really the same units. The reason for the difference is any
"idle" time that they system may have waiting for I/O to complete which does
not consume CPU time for your process, but does consume Elasped time.
For some instances of CPU intensive code (with no I/O of competing tasks),
the User + System ~= Elapsed. Also you have to take into account the
granularity of the clock when looking at numbers like 0.04. So serious
comparisons of timing, you want runs of at least 10s of seconds or more.
On 7/4/07, Stefan Grosse <[EMAIL PROTECTED]> wrote:
>
> Gabor Grothendieck wrote:
> >> set.seed(1)
> >> C <- sample(c("a", "b"), 10, replace = TRUE)
> >> system.time(s1 <- ifelse(C == "a", 1, -1))
> >>
> >user system elapsed
> >0.370.010.38
> >
> >> system.time(s2 <- 2 * (C == "a") - 1)
> >>
> >user system elapsed
> >0.020.000.02
> >
> > system.time(s1 <- ifelse(C == "a", 1, -1))
> user system elapsed
> 0.040.010.08
> > system.time(s2 <- 2 * (C == "a") - 1)
> user system elapsed
> 0 0 0
>
>
> I am just wondering: how comes the time does add up to 0.05 while
> elapsed states 0.08 on my system? (Vista+R2.5.1)
>
> Stefan
>
>
> -=-=-
> ... Time is an illusion, lunchtime doubly so. (Ford Prefect)
>
> __
> R-help@stat.math.ethz.ch mailing list
> 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.
>
--
Jim Holtman
Cincinnati, OH
+1 513 646 9390
What is the problem you are trying to solve?
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Re: [R] A More efficient method?
[Keith Alan Chamberlain]
>Is there a faster way than below to set a vector based on values
>from another vector? I'd like to call a pre-existing function for
>this, but one which can also handle an arbitrarily large number of
>categories. Any ideas?
>Cat=c('a','a','a','b','b','b','a','a','b') # Categorical variable
>C1=vector(length=length(Cat)) # New vector for numeric values
># Cycle through each column and set C1 to corresponding value of Cat.
>for(i in 1:length(C1)){
> if(Cat[i]=='a') C1[i]=-1 else C1[i]=1
>}
>C1
>[1] -1 -1 -1 1 1 1 -1 -1 1
>Cat
>[1] "a" "a" "a" "b" "b" "b" "a" "a" "b"
For handling an arbitrarily large number of categories, one may go
through a recoding vector, like this for the example above:
> Cat <- c('a', 'a', 'a', 'b', 'b', 'b', 'a', 'a', 'b')
> C1 <- c(a=-1, b=1)[Cat]
> C1
a a a b b b a a b
-1 -1 -1 1 1 1 -1 -1 1
--
François Pinard http://pinard.progiciels-bpi.ca
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Re: [R] A More efficient method?
This was in error since s3 was not set. The as.numeric in the calculation
of s3 can be omitted if its ok to have an integer rather than numeric result
and in that case its still faster yet.
> set.seed(1)
> C <- sample(c("a", "b"), 100, replace = TRUE)
> system.time({
+ s0 <- vector(length = length(C))
+ for(i in seq_along(C)) s0[i] <- if (C[i] == "a") 1 else -1
+ s0
+ })
user system elapsed
21.320.02 26.10
> system.time(s1 <- ifelse(C == "a", 1, -1))
user system elapsed
2.370.262.64
> system.time(s2 <- 2 * (C == "a") - 1)
user system elapsed
0.320.020.35
> system.time({tmp <- C == "a"; s3 <- as.numeric(tmp - !tmp)})
user system elapsed
0.280.020.31
> identical(s0, s1)
[1] TRUE
> identical(s0, s2)
[1] TRUE
> identical(s0, s3)
[1] TRUE
>
On 7/4/07, Gabor Grothendieck <[EMAIL PROTECTED]> wrote:
> In thinking about this a bit more I have found a slightly faster one still.
> See s3. Also I have added s0, the original solution, to the timings.
>
> > set.seed(1)
> > C <- sample(c("a", "b"), 100, replace = TRUE)
> > system.time({
> + s0 <- vector(length = length(C))
> + for(i in seq_along(C)) s0[i] <- if (C[i] == "a") 1 else -1
> + s0
> + })
> user system elapsed
> 21.750.02 25.99
> > system.time(s1 <- ifelse(C == "a", 1, -1))
> user system elapsed
> 2.320.172.54
> > system.time(s2 <- 2 * (C == "a") - 1)
> user system elapsed
> 0.290.020.32
> > system.time({tmp <- C == "a"; tmp - !tmp})
> user system elapsed
> 0.210.000.21
> > identical(s0, s1)
> [1] TRUE
> > identical(s0, s2)
> [1] TRUE
> > identical(s0, s3)
> [1] TRUE
>
> On 7/4/07, Gabor Grothendieck <[EMAIL PROTECTED]> wrote:
> > Here are two ways. The second way is more than 10x faster.
> >
> > > set.seed(1)
> > > C <- sample(c("a", "b"), 10, replace = TRUE)
> > > system.time(s1 <- ifelse(C == "a", 1, -1))
> > user system elapsed
> > 0.370.010.38
> > > system.time(s2 <- 2 * (C == "a") - 1)
> > user system elapsed
> > 0.020.000.02
> > > identical(s1, s2)
> > [1] TRUE
> >
> > On 7/4/07, Keith Alan Chamberlain <[EMAIL PROTECTED]> wrote:
> > > Dear Rhelpers,
> > >
> > > Is there a faster way than below to set a vector based on values from
> > > another vector? I'd like to call a pre-existing function for this, but one
> > > which can also handle an arbitrarily large number of categories. Any
> > > ideas?
> > >
> > > Cat=c('a','a','a','b','b','b','a','a','b') # Categorical variable
> > > C1=vector(length=length(Cat)) # New vector for numeric values
> > >
> > > # Cycle through each column and set C1 to corresponding value of Cat.
> > > for(i in 1:length(C1)){
> > >if(Cat[i]=='a') C1[i]=-1 else C1[i]=1
> > > }
> > >
> > > C1
> > > [1] -1 -1 -1 1 1 1 -1 -1 1
> > > Cat
> > > [1] "a" "a" "a" "b" "b" "b" "a" "a" "b"
> > >
> > > Sincerely,
> > > KeithC.
> > > Psych Undergrad, CU Boulder (US)
> > > RE McNair Scholar
> > >
> > > __
> > > R-help@stat.math.ethz.ch mailing list
> > > 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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Re: [R] A More efficient method?
In thinking about this a bit more I have found a slightly faster one still.
See s3. Also I have added s0, the original solution, to the timings.
> set.seed(1)
> C <- sample(c("a", "b"), 100, replace = TRUE)
> system.time({
+ s0 <- vector(length = length(C))
+ for(i in seq_along(C)) s0[i] <- if (C[i] == "a") 1 else -1
+ s0
+ })
user system elapsed
21.750.02 25.99
> system.time(s1 <- ifelse(C == "a", 1, -1))
user system elapsed
2.320.172.54
> system.time(s2 <- 2 * (C == "a") - 1)
user system elapsed
0.290.020.32
> system.time({tmp <- C == "a"; tmp - !tmp})
user system elapsed
0.210.000.21
> identical(s0, s1)
[1] TRUE
> identical(s0, s2)
[1] TRUE
> identical(s0, s3)
[1] TRUE
On 7/4/07, Gabor Grothendieck <[EMAIL PROTECTED]> wrote:
> Here are two ways. The second way is more than 10x faster.
>
> > set.seed(1)
> > C <- sample(c("a", "b"), 10, replace = TRUE)
> > system.time(s1 <- ifelse(C == "a", 1, -1))
> user system elapsed
> 0.370.010.38
> > system.time(s2 <- 2 * (C == "a") - 1)
> user system elapsed
> 0.020.000.02
> > identical(s1, s2)
> [1] TRUE
>
> On 7/4/07, Keith Alan Chamberlain <[EMAIL PROTECTED]> wrote:
> > Dear Rhelpers,
> >
> > Is there a faster way than below to set a vector based on values from
> > another vector? I'd like to call a pre-existing function for this, but one
> > which can also handle an arbitrarily large number of categories. Any ideas?
> >
> > Cat=c('a','a','a','b','b','b','a','a','b') # Categorical variable
> > C1=vector(length=length(Cat)) # New vector for numeric values
> >
> > # Cycle through each column and set C1 to corresponding value of Cat.
> > for(i in 1:length(C1)){
> >if(Cat[i]=='a') C1[i]=-1 else C1[i]=1
> > }
> >
> > C1
> > [1] -1 -1 -1 1 1 1 -1 -1 1
> > Cat
> > [1] "a" "a" "a" "b" "b" "b" "a" "a" "b"
> >
> > Sincerely,
> > KeithC.
> > Psych Undergrad, CU Boulder (US)
> > RE McNair Scholar
> >
> > __
> > R-help@stat.math.ethz.ch mailing list
> > 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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Re: [R] A More efficient method?
Dear Ted, You are correct in that factors are probably what I had in mind since I would be using them as predictors in a regression. I didn't know the syntax to get R to do the arithmetic. Many thanks to everyone who replied! Sincerely, KeithC. Psych Undergrad, CU Boulder (US) RE McNair Scholar __ R-help@stat.math.ethz.ch mailing list 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] A More efficient method?
#Given
Cat=c('a','a','a','b','b','b','a','a','b') # Categorical variable
#and defining
coding<-array(c(-1,1), dimnames=list(unique(Cat) ))
#(ie an array of values corresponding to your character array levels, and with
names set to those levels)
coding[Cat]
#does what you want.
>>> Keith Alan Chamberlain <[EMAIL PROTECTED]> 04/07/2007 14:44:44 >>>
Dear Rhelpers,
Is there a faster way than below to set a vector based on values from
another vector? I'd like to call a pre-existing function for this, but one
which can also handle an arbitrarily large number of categories. Any ideas?
Cat=c('a','a','a','b','b','b','a','a','b') # Categorical variable
C1=vector(length=length(Cat)) # New vector for numeric values
# Cycle through each column and set C1 to corresponding value of Cat.
for(i in 1:length(C1)){
if(Cat[i]=='a') C1[i]=-1 else C1[i]=1
}
C1
[1] -1 -1 -1 1 1 1 -1 -1 1
Cat
[1] "a" "a" "a" "b" "b" "b" "a" "a" "b"
Sincerely,
KeithC.
Psych Undergrad, CU Boulder (US)
RE McNair Scholar
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Re: [R] A More efficient method?
Gabor Grothendieck wrote:
>> set.seed(1)
>> C <- sample(c("a", "b"), 10, replace = TRUE)
>> system.time(s1 <- ifelse(C == "a", 1, -1))
>>
>user system elapsed
>0.370.010.38
>
>> system.time(s2 <- 2 * (C == "a") - 1)
>>
>user system elapsed
>0.020.000.02
>
> system.time(s1 <- ifelse(C == "a", 1, -1))
user system elapsed
0.040.010.08
> system.time(s2 <- 2 * (C == "a") - 1)
user system elapsed
0 0 0
I am just wondering: how comes the time does add up to 0.05 while
elapsed states 0.08 on my system? (Vista+R2.5.1)
Stefan
-=-=-
... Time is an illusion, lunchtime doubly so. (Ford Prefect)
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Re: [R] A More efficient method?
or
Cat <- c('a','a','a','b','b','b','a','a','b')
C1 <- (Cat=='a')*1
"ONKELINX,
Thierry"
"Keith Alan Chamberlain"
Sent by: <[EMAIL PROTECTED]>,
[EMAIL PROTECTED]
at.math.ethz.chcc
Subject
04/07/2007 17:17 Re: [R] A More efficient method?
Cat <- c('a','a','a','b','b','b','a','a','b')
C1 <- ifelse(Cat == 'a', -1, 1)
ir. Thierry Onkelinx
Instituut voor natuur- en bosonderzoek / Research Institute for Nature
and Forest
Cel biometrie, methodologie en kwaliteitszorg / Section biometrics,
methodology and quality assurance
Gaverstraat 4
9500 Geraardsbergen
Belgium
tel. + 32 54/436 185
[EMAIL PROTECTED]
www.inbo.be
Do not put your faith in what statistics say until you have carefully
considered what they do not say. ~William W. Watt
A statistical analysis, properly conducted, is a delicate dissection of
uncertainties, a surgery of suppositions. ~M.J.Moroney
> -Oorspronkelijk bericht-
> Van: [EMAIL PROTECTED]
> [mailto:[EMAIL PROTECTED] Namens Keith Alan
> Chamberlain
> Verzonden: woensdag 4 juli 2007 15:45
> Aan: r-help@stat.math.ethz.ch
> Onderwerp: [R] A More efficient method?
>
> Dear Rhelpers,
>
> Is there a faster way than below to set a vector based on
> values from another vector? I'd like to call a pre-existing
> function for this, but one which can also handle an
> arbitrarily large number of categories. Any ideas?
>
> Cat=c('a','a','a','b','b','b','a','a','b') # Categorical
variable
> C1=vector(length=length(Cat))# New vector for numeric values
>
> # Cycle through each column and set C1 to corresponding value of Cat.
> for(i in 1:length(C1)){
>if(Cat[i]=='a') C1[i]=-1 else C1[i]=1
> }
>
> C1
> [1] -1 -1 -1 1 1 1 -1 -1 1
> Cat
> [1] "a" "a" "a" "b" "b" "b" "a" "a" "b"
>
> Sincerely,
> KeithC.
> Psych Undergrad, CU Boulder (US)
> RE McNair Scholar
>
> __
> R-help@stat.math.ethz.ch mailing list
> 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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http://www.R-project.org/posting-guide.html
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Re: [R] A More efficient method?
Here are two ways. The second way is more than 10x faster.
> set.seed(1)
> C <- sample(c("a", "b"), 10, replace = TRUE)
> system.time(s1 <- ifelse(C == "a", 1, -1))
user system elapsed
0.370.010.38
> system.time(s2 <- 2 * (C == "a") - 1)
user system elapsed
0.020.000.02
> identical(s1, s2)
[1] TRUE
On 7/4/07, Keith Alan Chamberlain <[EMAIL PROTECTED]> wrote:
> Dear Rhelpers,
>
> Is there a faster way than below to set a vector based on values from
> another vector? I'd like to call a pre-existing function for this, but one
> which can also handle an arbitrarily large number of categories. Any ideas?
>
> Cat=c('a','a','a','b','b','b','a','a','b') # Categorical variable
> C1=vector(length=length(Cat)) # New vector for numeric values
>
> # Cycle through each column and set C1 to corresponding value of Cat.
> for(i in 1:length(C1)){
>if(Cat[i]=='a') C1[i]=-1 else C1[i]=1
> }
>
> C1
> [1] -1 -1 -1 1 1 1 -1 -1 1
> Cat
> [1] "a" "a" "a" "b" "b" "b" "a" "a" "b"
>
> Sincerely,
> KeithC.
> Psych Undergrad, CU Boulder (US)
> RE McNair Scholar
>
> __
> R-help@stat.math.ethz.ch mailing list
> 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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Re: [R] A More efficient method?
On 04-Jul-07 13:44:44, Keith Alan Chamberlain wrote:
> Dear Rhelpers,
>
> Is there a faster way than below to set a vector based on values
> from another vector? I'd like to call a pre-existing function for
> this, but one which can also handle an arbitrarily large number
> of categories. Any ideas?
>
> Cat=c('a','a','a','b','b','b','a','a','b')# Categorical variable
> C1=vector(length=length(Cat)) # New vector for numeric values
>
># Cycle through each column and set C1 to corresponding value of Cat.
> for(i in 1:length(C1)){
> if(Cat[i]=='a') C1[i]=-1 else C1[i]=1
> }
>
> C1
> [1] -1 -1 -1 1 1 1 -1 -1 1
> Cat
> [1] "a" "a" "a" "b" "b" "b" "a" "a" "b"
> Cat=c('a','a','a','b','b','b','a','a','b')
> Cat=="b"
[1] FALSE FALSE FALSE TRUE TRUE TRUE FALSE FALSE TRUE
> (Cat=="b") - 0.5
[1] -0.5 -0.5 -0.5 0.5 0.5 0.5 -0.5 -0.5 0.5
> 2*((Cat=="b") - 0.5)
[1] -1 -1 -1 1 1 1 -1 -1 1
to give one example of a way to do it. But you don't say why you
really want to do this. You may really want factors. And what do
you want to see if there is "an arbitrarily large number of
categories"?
For instance:
> factor(Cat,labels=c(-1,1))
[1] -1 -1 -1 1 1 1 -1 -1 1
but this is not a vector, but a "factor" object. To get the vector,
you need to convert Cat to an integer:
> as.integer(factor(Cat))
[1] 1 1 1 2 2 2 1 1 2
where (unless you've specified otherwise in factor()) the values
will correspond to the elements of Cat in "natural" order, in this
case first "a" (-> 1), then "b" (-> 2).
E.g.
> Cat2<-c("a","a","c","b","a","b")
> as.integer(factor(Cat2))
[1] 1 1 3 2 1 2
so, with C2<-as.integer(factor(Cat2)), you get a vector of distinct
integers 91,2,3) for the distinct levels ("a","b","c") of Cat2.
If you want integer values for these levels, you can write a function
to change them.
Hoping this helps to beark the ice!
Ted.
E-Mail: (Ted Harding) <[EMAIL PROTECTED]>
Fax-to-email: +44 (0)870 094 0861
Date: 04-Jul-07 Time: 16:44:20
-- XFMail --
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Re: [R] A More efficient method?
> Cat=c('a','a','a','b','b','b','a','a','b')# Categorical variable
> C1=vector(length=length(Cat)) # New vector for numeric values
>
> # Cycle through each column and set C1 to corresponding value of Cat.
> for(i in 1:length(C1)){
> if(Cat[i]=='a') C1[i]=-1 else C1[i]=1
> }
>
> C1
> [1] -1 -1 -1 1 1 1 -1 -1 1
> Cat
> [1] "a" "a" "a" "b" "b" "b" "a" "a" "b"
>
>
how about:
Cat<-c('a','a','a','b','b','b','a','a','b')
c1<- -2*(Cat=="a")+1
-=-=-
... Time is an illusion, lunchtime doubly so. (Ford Prefect)
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Re: [R] A More efficient method?
C1 <- rep(-1, length(Cat))
C1[Cat == "b"]] <- 1
b
On Jul 4, 2007, at 9:44 AM, Keith Alan Chamberlain wrote:
> Dear Rhelpers,
>
> Is there a faster way than below to set a vector based on values from
> another vector? I'd like to call a pre-existing function for this,
> but one
> which can also handle an arbitrarily large number of categories.
> Any ideas?
>
> Cat=c('a','a','a','b','b','b','a','a','b')# Categorical variable
> C1=vector(length=length(Cat)) # New vector for numeric values
>
> # Cycle through each column and set C1 to corresponding value of Cat.
> for(i in 1:length(C1)){
> if(Cat[i]=='a') C1[i]=-1 else C1[i]=1
> }
>
> C1
> [1] -1 -1 -1 1 1 1 -1 -1 1
> Cat
> [1] "a" "a" "a" "b" "b" "b" "a" "a" "b"
>
> Sincerely,
> KeithC.
> Psych Undergrad, CU Boulder (US)
> RE McNair Scholar
>
> __
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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.
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Re: [R] A More efficient method?
Cat <- c('a','a','a','b','b','b','a','a','b')
C1 <- ifelse(Cat == 'a', -1, 1)
ir. Thierry Onkelinx
Instituut voor natuur- en bosonderzoek / Research Institute for Nature
and Forest
Cel biometrie, methodologie en kwaliteitszorg / Section biometrics,
methodology and quality assurance
Gaverstraat 4
9500 Geraardsbergen
Belgium
tel. + 32 54/436 185
[EMAIL PROTECTED]
www.inbo.be
Do not put your faith in what statistics say until you have carefully
considered what they do not say. ~William W. Watt
A statistical analysis, properly conducted, is a delicate dissection of
uncertainties, a surgery of suppositions. ~M.J.Moroney
> -Oorspronkelijk bericht-
> Van: [EMAIL PROTECTED]
> [mailto:[EMAIL PROTECTED] Namens Keith Alan
> Chamberlain
> Verzonden: woensdag 4 juli 2007 15:45
> Aan: r-help@stat.math.ethz.ch
> Onderwerp: [R] A More efficient method?
>
> Dear Rhelpers,
>
> Is there a faster way than below to set a vector based on
> values from another vector? I'd like to call a pre-existing
> function for this, but one which can also handle an
> arbitrarily large number of categories. Any ideas?
>
> Cat=c('a','a','a','b','b','b','a','a','b')# Categorical variable
> C1=vector(length=length(Cat)) # New vector for numeric values
>
> # Cycle through each column and set C1 to corresponding value of Cat.
> for(i in 1:length(C1)){
> if(Cat[i]=='a') C1[i]=-1 else C1[i]=1
> }
>
> C1
> [1] -1 -1 -1 1 1 1 -1 -1 1
> Cat
> [1] "a" "a" "a" "b" "b" "b" "a" "a" "b"
>
> Sincerely,
> KeithC.
> Psych Undergrad, CU Boulder (US)
> RE McNair Scholar
>
> __
> R-help@stat.math.ethz.ch mailing list
> 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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[R] A More efficient method?
Dear Rhelpers,
Is there a faster way than below to set a vector based on values from
another vector? I'd like to call a pre-existing function for this, but one
which can also handle an arbitrarily large number of categories. Any ideas?
Cat=c('a','a','a','b','b','b','a','a','b') # Categorical variable
C1=vector(length=length(Cat)) # New vector for numeric values
# Cycle through each column and set C1 to corresponding value of Cat.
for(i in 1:length(C1)){
if(Cat[i]=='a') C1[i]=-1 else C1[i]=1
}
C1
[1] -1 -1 -1 1 1 1 -1 -1 1
Cat
[1] "a" "a" "a" "b" "b" "b" "a" "a" "b"
Sincerely,
KeithC.
Psych Undergrad, CU Boulder (US)
RE McNair Scholar
__
R-help@stat.math.ethz.ch mailing list
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
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Re: [R] A More efficient method?
Keith Alan Chamberlain Colorado.EDU> writes:
> Cat=c('a','a','a','b','b','b','a','a','b')# Categorical variable
> C1=vector(length=length(Cat)) # New vector for numeric values
> for(i in 1:length(C1)){
> if(Cat[i]=='a') C1[i]=-1 else C1[i]=1
> }
>
> C1
> [1] -1 -1 -1 1 1 1 -1 -1 1
> Cat
> [1] "a" "a" "a" "b" "b" "b" "a" "a" "b"
ifelse(Cat == "a", -1, 1)
[1] -1 -1 -1 1 1 1 -1 -1 1
HTH
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