indexing question

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How about this:
data(ToothGrowth)
ls()
[1] "ToothGrowth"
data <- function(x){invisible(NULL)}
data(ToothGrowth)
ls()
[1] "data"

From: baptiste auguie <ba208 at exeter.ac.uk>
To: Dimitris Rizopoulos <d.rizopoulos at erasmusmc.nl>
Date: Tue, 13 Jan 2009 09:38:09 +0000
Subject: Re: [R] indexing question

you can also look at subset,

       my.data.frame <- data.frame(a=rnorm(10),
b=factor(sample(letters[1:4], 10, replace=T)))
       str(my.data.frame)
       my.data.frame[my.data.frame$b == "a", ]
       subset(my.data.frame, b == "a")

by the way, it is probably safer not to use "data" as a variable name as it
is also a function.

I've often wondered about this. The thing is, I've never run into a problem
with this. For example:

ls()
character(0)
data(ToothGrowth)
ls()
[1] "ToothGrowth"
rm(ToothGrowth)
ls()
character(0)
data <- data.frame(1:10, 101:110)
data(ToothGrowth) #works just the same
ls()
[1] "data"        "ToothGrowth"

In this example the data command works just the same the second time, even
though I have a data.frame named data. Can someone give an example where
this causes a problem?

Thanks,
Ista

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______________________________________________
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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.

Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem that you are trying to solve?
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R does understand the class of the object so that it knows it should
not try to call the dataframe 'data' if the function 'data' is being
called.  It is probably best to avoid what would be termed "reserved"
words just to prevent mistakes in the future.  How about calling them
"Data"?

On Tue, Jan 13, 2009 at 10:23 AM, jim holtman <jholtman at gmail.com> wrote:
How about this:

data(ToothGrowth)
ls()
[1] "ToothGrowth"
data <- function(x){invisible(NULL)}
data(ToothGrowth)
ls()
[1] "data"

Yep, that sure does cause a problem alright. Is it the case that that
problems arise when you name a function with the same name as an existing
function? Or are there cases where naming data.frames, vectors, matrices,
etc. can also cause problems?

I hope I'm not being annoying -- I'm just trying to determine if I need to
break my habit of naming data.frames "data".

Thanks,
Ista

On Tue, Jan 13, 2009 at 9:53 AM, Ista Zahn <istazahn at gmail.com> wrote:
From: baptiste auguie <ba208 at exeter.ac.uk>
To: Dimitris Rizopoulos <d.rizopoulos at erasmusmc.nl>
Date: Tue, 13 Jan 2009 09:38:09 +0000
Subject: Re: [R] indexing question

you can also look at subset,

       my.data.frame <- data.frame(a=rnorm(10),
b=factor(sample(letters[1:4], 10, replace=T)))
       str(my.data.frame)
       my.data.frame[my.data.frame$b == "a", ]
       subset(my.data.frame, b == "a")

by the way, it is probably safer not to use "data" as a variable name
as it
is also a function.

I've often wondered about this. The thing is, I've never run into a
problem
with this. For example:

ls()
character(0)
data(ToothGrowth)
ls()
[1] "ToothGrowth"
rm(ToothGrowth)
ls()
character(0)
data <- data.frame(1:10, 101:110)
data(ToothGrowth) #works just the same
ls()
[1] "data"        "ToothGrowth"

In this example the data command works just the same the second time,
even
though I have a data.frame named data. Can someone give an example where
this causes a problem?

Thanks,
Ista

       [[alternative HTML version deleted]]

______________________________________________
R-help at r-project.org 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 that you are trying to solve?

Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem that you are trying to solve?
There are real examples; they are all fairly obscure.  It can't be a big problem because the standard formal argument name for a data frame in modelling and graphics functions is 'data'.  That's actually a more serious problem than the function called data() -- having local and global variables with the same name won't confuse R, but it can easily confuse you.

Possibilities for R getting confused include
  1. The functions for environment access by name, eg exists(), get(), don't by default check the type of the argument.
  2. bquote() and substitute() substitute before evaluating and could get confused.

There used to be real problems in S when certain function names were used as data names.  Then there was a period of aversive conditioning by irritating warnings. As a result, I still avoid 'c' and 't' as variable names.

You could call your data frames 'df' -- many of the people who complain about 'data' don't realise that df() is the density function of the F distribution :)

      -thomas

On Tue, Jan 13, 2009 at 10:23 AM, jim holtman <jholtman at gmail.com> wrote:

How about this:

data(ToothGrowth)
ls()
[1] "ToothGrowth"
data <- function(x){invisible(NULL)}
data(ToothGrowth)
ls()
[1] "data"