Re: [R] Using subset() in a user-defined function

From: Tobin, Jared <TobinJR_at_DFO-MPO.GC.CA>
Date: Thu, 14 Jun 2007 12:45:08 -0230

I should mention the idea I worked on yesterday was cat()ing together the appropriate condition strings and then ideally printing that entire concatenated string into the subset argument. However, as far as I know, cat() only prints directly on the console and cannot be used to substitute input text into a function, so I scrapped that idea.

Just figured I'd mention that in case there does happen to be a way to do such a thing, and someone knows of a way offhand.

--

jared tobin, student research assistant
dept. of fisheries and oceans
tobinjr_at_dfo-mpo.gc.ca

-----Original Message-----
From: Tobin, Jared 
Sent: Thursday, June 14, 2007 12:28 PM
To: 'Duncan Murdoch'
Cc: r-help_at_stat.math.ethz.ch
Subject: RE: [R] Using subset() in a user-defined function

Thanks for the quick response, Duncan.

The given code doesn't seem to work, and possibly due to this reason I
found in the online help for missing() (if I understand it correctly):

"Currently missing() can only be used in the immediate body of the
function that defines the argument, not in the body of a nested function
or a local call. This may change in the future."

So as I understand it, missing() cannot refer to the arguments of
function1 if it is used in an argument of subset()?  It seems to remain
a promising function for this situation regardless, but I'm not sure how
I could implement it into the subset() arguments offhand.

--

jared tobin, student research assistant
dept. of fisheries and oceans
tobinjr_at_dfo-mpo.gc.ca

-----Original Message-----
From: Duncan Murdoch [mailto:murdoch_at_stats.uwo.ca]
Sent: Thursday, June 14, 2007 11:28 AM
To: Tobin, Jared
Cc: r-help_at_stat.math.ethz.ch
Subject: Re: [R] Using subset() in a user-defined function

On 6/14/2007 9:38 AM, Tobin, Jared wrote:

> Hello,
>
> I'm having a problem with using subset() inside a function I'm
writing.
> Ignoring everything else in the function, the problem can be
> illustrated by (where master.frame is the data frame I'm using):
>
>
> function1 <- function(arg1="", arg2="", arg3=""){
>
> temp.frame <- subset(master.frame, a == arg1 & b == arg2 & c ==
> arg3)
>
> }
>
>
> This works fine if the user specifies all arguments, but if any one or

> more of the arguments isn't specified, say arg1 for example, the
> subset is empty because subset() goes looking for values of a == "" in

> master.frame, and there are none. I want it to work such that if an
> argument is not specified, it is not included in what subset() goes
> looking for. So if I were to input:
>
> function1(arg2=5, arg3=6)
>
> then in function1, the subset command will look like
>
> temp.frame <- subset(master.frame, b == 5 & c == 6)
>
>
> Any suggestions would be much appreciated.
Code it like this: subset(master.frame, (missing(arg1) | a == arg1) & (missing(arg2) | b == arg2) & (missing(arg3) | c == arg3)) I haven't tried this, and I forget what happens in subset() if you pass it a subset of the wrong length, so it might fail if all args are missing, but otherwise I think it should work. It does depend on defaults for the args existing and not causing errors in the equality tests (it's not using shortcut evaluation). Duncan Murdoch ______________________________________________ R-help_at_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.
Received on Thu 14 Jun 2007 - 16:01:42 GMT

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