[R] lapply and paste

[R. Michael Weylandt <michael.weylandt@gmail.com>]

Yes, there are non-vectorized functions e.g, integrate(), or you can use lapply() to apply a vectorized function to each element of a list (which is not what suff was) individually:

x <- list(1:3, 1:4, 1:5, 2:7)
mean(x) # bad
lapply(x, mean) #good

Michael

On Mar 28, 2012, at 2:44 PM, Ed Siefker <ebs15242 at gmail.com> wrote:

> Thank you, I was confused about that.  What exactly is lapply for then,
> if R handles this kind of thing automatically?  Are there functions that are
> not "vectorized"?
> 
> 
> On Wed, Mar 28, 2012 at 1:37 PM, R. Michael Weylandt
> <michael.weylandt at gmail.com> wrote:
>> I think you're confused about the need for lapply -- paste is
>> vectorized so this
>> 
>> paste("filename_", suff, ".ext", sep = "")
>> 
>> will work. But if you want to use lapply (for whatever reason) try this:
>> 
>> lapply(suff, function(x) paste("filename_", x, ".ext", sep = "")
>> 
>> Michael
>> 
>> On Wed, Mar 28, 2012 at 2:31 PM, Ed Siefker <ebs15242 at gmail.com> wrote:
>>> I have a list of suffixes I want to turn into file names with extensions.
>>> 
>>> suff<- c("C1", "C2", "C3")
>>> paste("filename_", suff[[1]], ".ext", sep="")
>>> [1] "filename_C1.ext"
>>> 
>>> How do I use lapply() on that call to paste()?
>>> What's the right way to do this:
>>> 
>>> filenames <-  lapply(suff, paste, ...)
>>> 
>>> ?
>>> 
>>> Can I have lapply() reorder the arguments to FUN?
>>> 
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