R help - Nov 2009 - Is there an variant of apply() that does not return anything?

There are a few version of apply() (e.g., lapply(), sapply()). I'm
wondering if there is one that does not return anything but just
silently apply a function to the list argument.

For example, the plot function is applied to each element in 'alist'.
It is redundant to return anything from apply.

apply(alist,function(x){ plot each element of alist})

On Nov 20, 2009, at 10:21 AM, Peng Yu wrote:
> There are a few version of apply() (e.g., lapply(), sapply()). I'm
> wondering if there is one that does not return anything but just
> silently apply a function to the list argument.
>
> For example, the plot function is applied to each element in
'alist'.
> It is redundant to return anything from apply.
>
> apply(alist,function(x){ plot each element of alist})


Just use a for() loop. If you are plotting things, the performance  
bottleneck is not going to be in the loop.

Sometimes, we get too anal about avoiding for() loops.

HTH,

Marc Schwartz

On Thu, Nov 19, 2009 at 2:21 PM, Peng Yu <pengyu.ut at gmail.com>
wrote:
> There are a few version of apply() (e.g., lapply(), sapply()). I'm
> wondering if there is one that does not return anything but just
> silently apply a function to the list argument.
>
> For example, the plot function is applied to each element in
'alist'.
> It is redundant to return anything from apply.
>
> apply(alist,function(x){ plot each element of alist})
Take a look at the l_ply(), a_ply() and d_ply() functions from
Hadley's "plyr" package.  They are a refinement and extension to
the
apply family of functions and the underscore, "_", in the function
names indicates that they have no return value.


-Charlie

invisible(apply(...))

On Thu, Nov 19, 2009 at 5:21 PM, Peng Yu <pengyu.ut at gmail.com>
wrote:
> There are a few version of apply() (e.g., lapply(), sapply()). I'm
> wondering if there is one that does not return anything but just
> silently apply a function to the list argument.
>
> For example, the plot function is applied to each element in
'alist'.
> It is redundant to return anything from apply.
>
> apply(alist,function(x){ plot each element of alist})
>
> ______________________________________________
> 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?

I want to use both the name and the content. Although, I could do the
following thing.

for(x in names(List)) {
  do some thing with x
  do some thing with List[[x]]
}

However, I'd prefer something like the following if R offers such
functionality. But it seems not.

for(x in List) {
  do something with the name of x
  do something with x
}

On Fri, Nov 20, 2009 at 4:35 PM, Jorge Ivan Velez
<jorgeivanvelez at gmail.com> wrote:
> If I understood correctly
> for(x in names(List)) print(x)
> should do what you asked.
> HTH, Jorge
>
> On Thu, Nov 19, 2009 at 5:31 PM, Peng Yu <> wrote:
>>
>> On Thu, Nov 19, 2009 at 4:27 PM, Marc Schwartz <marc_schwartz at
me.com>
>> wrote:
>> > On Nov 20, 2009, at 10:21 AM, Peng Yu wrote:
>> >
>> >> There are a few version of apply() (e.g., lapply(), sapply()).
I'm
>> >> wondering if there is one that does not return anything but
just
>> >> silently apply a function to the list argument.
>> >>
>> >> For example, the plot function is applied to each element in
'alist'.
>> >> It is redundant to return anything from apply.
>> >>
>> >> apply(alist,function(x){ plot each element of alist})
>> >
>> >
>> >
>> > Just use a for() loop. If you are plotting things, the performance
>> > bottleneck is not going to be in the loop.
>> >
>> > Sometimes, we get too anal about avoiding for() loops.
>>
>> Is there a way to get the name of the list in the loop body?
>>
>> > List=list(a='c',b='x',e='q')
>> > for(x in List) { print(x) }
>> [1] "c"
>> [1] "x"
>> [1] "q"
>>
>> ______________________________________________
>> 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.
>
>