Sam:
On Wed, Feb 8, 2012 at 12:56 PM, Sam Steingold <s...@gnu.org> wrote:
> To be clear, I can do that with nested for loops:
>
> v <- c("A1B2","A3C4","B5","C6A7B8")
> l <- strsplit(gsub("(.{2})","\\1,",v),",")
> d <- data.frame(A=vector(length=4,mode="integer"),
> B=vector(length=4,mode="integer"),
> C=vector(length=4,mode="integer"))
>
> for (i in 1:length(l)) {
> l1 <- l[[i]]
> for (j in 1:length(l1)) {
> d[[substring(l1[j],1,1)]][i] <- as.numeric(substring(l1[j],2,2))
> }
> }
>
>
> but I am afraid that handling 1,000,000 (=length(unlist(l))) strings in
> a loop will kill me.
Well, that depends on how "dead" you can stand being. Try it with a
1000 entry subvector and see how bad it gets. A few extra minutes of
computing time to save many more minutes of programming time seems a
reasonable tradeoff. Alternatively, see ?compile to compile your
solution into bytecode, which might give a few fold reduction in time
(or not). The calculation could also be parallelized using the
parallel package, I'm sure.
-- Bert
>
>
>> * Sam Steingold <f...@tah.bet> [2012-02-08 15:34:38 -0500]:
>>
>> Suppose I have a vector of strings:
>> c("A1B2","A3C4","B5","C6A7B8")
>> [1] "A1B2" "A3C4" "B5" "C6A7B8"
>> where each string is a sequence of <column><value> pairs
>> (fixed width, in this example both value and name are 1 character, in
>> reality the column name is 6 chars and value is 2 digits).
>> I need to convert it to a data frame:
>> data.frame(A=c(1,3,0,7),B=c(2,0,5,8),C=c(0,4,0,6))
>> A B C
>> 1 1 2 0
>> 2 3 0 4
>> 3 0 5 0
>> 4 7 8 6
>>
>> how do I do that?
>> thanks.
>
> --
> Sam Steingold (http://sds.podval.org/) on Ubuntu 11.10 (oneiric) X
> 11.0.11004000
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--
Bert Gunter
Genentech Nonclinical Biostatistics
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