Suggestions for vectorizing/double loop

Hi

In your case if you want to rename abot 600 items and your doble loop works it is not worth to vectorize it. However if you want to repeat such task often and you expect much bigger number of files vectorizing can speed things up and make them cleaner.

Although I must admit that I do not understand what your commands should actually do. AFAICU the list is the same before and after your "double" loop.

Cheers
Petr

-----Original Message-----
From: R-help [mailto:r-help-bounces at r-project.org] On Behalf Of Luanna
Dixson
Sent: Monday, January 23, 2017 1:28 PM
To: r-help at r-project.org
Subject: [R] Suggestions for vectorizing/double loop

I need to rename a bunch of files, by searching for string matches in a list.
Each list element containings a character with the old filename that I want to
match to, and the new file name that I want to rename by.

For instance, here filename '1001.xls' should match to list[[1]]$oldname and I
want to rename it to 'newa.xls' from list[[1]]$newname.

The actual new file names I have will feature a random alphanumeric number
and the list will have a length of ~600.


# files I want to rename

files with old file name =c('1001.xls', '1002.xls')

# list with old file names and new file names

oldnames=c('1001', '1002', '1003')

newnames=c('newa', 'newb', 'newc')

df=data.frame(oldnames,newnames)

list <- split(df, rownames(df))


# turn list elements in character

for(i in 1:length(list)) list[[i]]$oldnames=as.character(list[[i]]$oldnames)

for(i in 1:length(list)) list[[i]]$newnames=as.character(list[[i]]$newnames)


I heard that it would be better to vectorize this than trying to do a double
loop so if someone could give me a hint about how to do this I would be very
grateful!

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