I echo Duncan's plea.
But I can easily resolve one question:
"What's with "with? It is one function I do not use because I find it
incomprehensible. "
Consider:
## first, clear the workspace, also known as the Global environment
> rm(list=ls())
## now create a data frame (or list or environment or...) containing
objects named "x" and "w"
> d <- data.frame(x=1:3,w=5:7)
## now define a different "x" in the workspace
> x <- 4:6
>
> ## The following will produce an error, because there is no "w" in the
> workspace
> ##
> w
Error: object 'w' not found
>
> ## But this won't, since with() tells it's expression to first search in d.
>
> with(d,w)
[1] 5 6 7
>
> ## similarly
>
> ##error
> x+w
Error: object 'w' not found
>
> ## But
> with(d, x+w)
[1] 6 8 10
>
> ## In general, the second argument of d can be any expression that you could
> type at the console.
>
> ## If something can't be found in d, it will be looked for in d's "parent"
> environment, which is more involved than I want to get here. But:
>
> y <- 5
>
> with(d, x+y) ## used x in d, and y in the workspace.
[1] 6 7 8
HTH
Bert
Bert Gunter
"The trouble with having an open mind is that people keep coming along
and sticking things into it."
-- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )
On Thu, Sep 8, 2016 at 3:57 PM, Carl Sutton via R-help
<r-help@r-project.org> wrote:
> Hi
> I have doing the R-exercises to improve my R programming capabilities.
> Data.frame exercise 4 showed me that I have a language problem. Here's the
> problem and my "solution".
> # Exercise 4# Create a simple data frame from 3 vectors. Order the entire
> data frame by the# first column.df2 <- data.frame(a = 5:1,b = letters[1:5],
> c = runif(5))order(df2$a) Naturally the order function did nothing.
> Per "help"Description
> order returns a permutation which rearranges its first argument into
> ascending or descending order, breaking ties by further arguments. sort.list
> is the same, using only one argument.See the examples for how to use these
> functions to sort data frames, etc.
> Usage
> order(..., na.last = TRUE, decreasing = FALSE, method = c("shell",
> "radix"))
> sort.list(x, partial = NULL, na.last = TRUE, decreasing = FALSE,
> method = c("shell", "quick", "radix"))Arguments
> ... a sequence of numeric, complex, character or logical vectors, all of the
> same length, or a classed R object.
> Well, doesn't ... mean any legal object? I gave it a legal object and got
> nada.And the answer absolutely has me screaming "Say
> What"df2[with(df2,order(a)),]
>
> What's with "with? It is one function I do not use because I find it
> incomprehensible. To witEvaluate an R expression in an environment
> constructed from data, possibly modifying (a copy of) the original data.
>
> First of all, if I'm not modifying data (or as a subset activity creating
> data), why an I doing whatever it is I'm doing? ("possibly modifying (a copy
> of) the original data.")
> Evaluate. According to the thesarus A) assess(v), b) appraise, c) gage.
> OK, am I in a safe area? I'll evaluate that. Do I desire future social
> contact with this person? I'll evaluate that.In no way do I ever evaluate an
> equation. I may attempt to solve it. I may do a computer program to do the
> calculations and return a result. I will probably evaluate the result as to
> whether or not it helps solve the problem. Think in terms of an income tax
> return. But evaluate an R expression? No clue what that might mean.
> The remainder of the definition is also obtuse. an R expression in an
> environment constructed from data. Why would one make an environment without
> data? Obviously I am missing the point. My own created function makes a new
> environment, but I only created it to crunch numbers. If it doesn't crunch
> numbers it's useless.
> The point is, I do not understand the definition of "with" and thus have no
> idea how to use it. I guess computerese is analogous to taxlawese. Familiar
> words have entirely different meanings.
> Carl Sutton CPA
>
> [[alternative HTML version deleted]]
>
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