Vining, Kelly wrote:
>
> Dear UseRs,
>
> I have a data frame that looks like this:
>
> head(test2)
> attributes start end StemExplant Callus RegenPlant
> 1 LTR_Unknown 120 535 3.198 1.931 1.927
> 3 LTR_Unknown 2955 3218 0.541 0.103 0.613
> 6 LTR_Unknown 6210 6423 6.080 4.650 9.081
> 9 LTR_Unknown 9658 10124 0.238 0.117 0.347
> 14 LTR_Unknown 14699 14894 3.545 3.625 2.116
> 25 LTR_Unknown 33201 33474 1.275 1.194 0.591
>
>
> I need to subtract each value in the "end" column from its corresponding
> value in the "start" column, then append that difference as a new column
> in this data frame.
>
> It seems like apply could be the way to approach this, but I can't see any
> easy way to designate "difference" as a function, like, say, sum or mean.
> Plus, all the apply/lapply examples I'm looking at seem to depend on a
> data frame being just the two columns on which to operate, without any way
> to designate which columns to use in the function(x,y) part of an lapply
> statement. Another alternative would be a for loop, but when I try this:
>
> for(i in 1:nrow(test2)) {
> testout[i] <- (test2$end[i] - test2$start[i])
> }
>
> I get an error. So I'm stuck at the first step here. I think that once I
> can figure out how to get the differences, I can use cbind to append the
> data frame. But if there is a better way to do it, I'd like to know that
> as well.
>
> Any help is appreciated.
>
> --Kelly V.
> ______________________________________________
> R-help@ mailing list
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> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
IS this what you are looking for?
# Data
lines <- "attributes start end StemExplant Callus RegenPlant
LTR_Unknown 120 535 3.198 1.931 1.927
LTR_Unknown 2955 3218 0.541 0.103 0.613
LTR_Unknown 6210 6423 6.080 4.650 9.081
LTR_Unknown 9658 10124 0.238 0.117 0.347
LTR_Unknown 14699 14894 3.545 3.625 2.116
LTR_Unknown 33201 33474 1.275 1.194 0.591"
d = read.table(textConnection(lines), header=TRUE)
# Create new variable
d$new=d$end - d$start
print(d)
attributes start end StemExplant Callus RegenPlant new
1 LTR_Unknown 120 535 3.198 1.931 1.927 415
2 LTR_Unknown 2955 3218 0.541 0.103 0.613 263
3 LTR_Unknown 6210 6423 6.080 4.650 9.081 213
4 LTR_Unknown 9658 10124 0.238 0.117 0.347 466
5 LTR_Unknown 14699 14894 3.545 3.625 2.116 195
6 LTR_Unknown 33201 33474 1.275 1.194 0.591 273
HTH
Pete
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