Re: [R] concatenate vector after strsplit()

[David Winsemius]

On Feb 20, 2011, at 12:49 PM, David Winsemius wrote:

On Feb 20, 2011, at 11:13 AM, Robert Baer wrote:

ls is a list of character vectors created by strsplit()

I want to concatenate  the 1st 4 character elements of each list  
item as a new vector called file.  I admit to being confused about  
list syntax even after numerous readings.

Here's what I tried:

ls <- list(c("Focused", "10k", "A12", "t04.tif", "+", "µm"),  
c("Focused",
"10k", "A12", "t08.tif", "+", "µm"), c("Focused", "10k", "A12",
"t12.tif", "+", "µm"), c("Focused", "10k", "A12", "t16.tif",
"+", "µm"), c("Focused", "10k", "A12", "t20.tif", "+", "µm"),
  c("Focused", "10k", "A12", "t24.tif", "+", "µm"), c("Focused",
  "10k", "A12", "t36.tif", "+", "µm"), c("Focused", "10k",
  "A12", "t48.tif", "+", "µm"), c("Focused", "10k", "B12",
  "t04.tif", "+", "µm"), c("Focused", "10k", "B12", "t08.tif",
  "+", "µm"))

Perhaps:

> sapply(ls1, paste, collapse="")
[1] "Focused10kA12t04.tif+µm" "Focused10kA12t08.tif+µm"
[3] "Focused10kA12t12.tif+µm" "Focused10kA12t16.tif+µm"
[5] "Focused10kA12t20.tif+µm" "Focused10kA12t24.tif+µm"
[7] "Focused10kA12t36.tif+µm" "Focused10kA12t48.tif+µm"
[9] "Focused10kB12t04.tif+µm" "Focused10kB12t08.tif+µm"

(I changed the name and will not illustrate its assignment to  
"file". It is generally considered poor programming practice  to use  
function names for variable objects.)

I suppose it would be better practice on my part to read the question  
more thoroughly:

> sapply(lapply(ls1, "[", 1:4), paste, collapse="")
 [1] "Focused10kA12t04.tif" "Focused10kA12t08.tif"
 [3] "Focused10kA12t12.tif" "Focused10kA12t16.tif"
 [5] "Focused10kA12t20.tif" "Focused10kA12t24.tif"
 [7] "Focused10kA12t36.tif" "Focused10kA12t48.tif"
 [9] "Focused10kB12t04.tif" "Focused10kB12t08.tif"

--
David.

# Test the waters with one element
cat(unlist(ls[1])[1:4])      # WHY DOES THE COMMAND PROMPT NOT  
APPEAR ON NEXT LINE AS USUAL???

# Appears to work except for command prompt glitch

# Attempts to use tapply() don't get me anywhere
file <- tapply(unlist(ls), list(1:length(unlist(ls))),  
cat(unlist(ls[1])[1:4]))

I'm grateful for an approach to putting my vector together, but I'd  
also love to understand the headache I've apparently given the  
command parser.  I'm apparently doing some "no no".

Thanks,

Rob

R.Version()
$platform
[1] "i386-pc-mingw32"

$arch
[1] "i386"

$os
[1] "mingw32"

$system
[1] "i386, mingw32"

$status
[1] ""

$major
[1] "2"

$minor
[1] "12.1"

$year
[1] "2010"

$month
[1] "12"

$day
[1] "16"

$`svn rev`
[1] "53855"

$language
[1] "R"

$version.string
[1] "R version 2.12.1 (2010-12-16)"



David Winsemius, MD
West Hartford, CT

______________________________________________
R-help@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.