[R] conditional filling of data.frame - improve code

[Jeff Newmiller]

Use merge.

expts <- read.csv( text =
"expt,sample
ex1,sample1-1
ex1,sample1-2
ex2,sample2-1
ex2,sample2-2
ex2,sample2-3
", header=TRUE, as.is=TRUE )

mydata <- data.frame(sample = c("sample2-2", "sample2-3", "sample1-1", "sample1-1", "sample1-1", "sample2-1"))

merge( mydata, expts, by="sample", all.x=TRUE )


On March 10, 2022 7:50:23 AM PST, Ivan Calandra <ivan.calandra using rgzm.de> wrote:
>Dear useRs,
>
>I would like to improve my ugly (though working) code, but I think I 
>need a completely different approach and I just can't think out of my box!
>
>I have some external information about which sample(s) belong to which 
>experiment. I need to get that manually into R (either typing directly 
>in a script or read a CSV file, but that makes no difference):
>exp <- list(ex1 = c("sample1-1", "sample1-2"), ex2 = c("sample2-1", 
>"sample2-2" , "sample2-3"))
>
>Then I have my data, only with the sample IDs:
>mydata <- data.frame(sample = c("sample2-2", "sample2-3", "sample1-1", 
>"sample1-1", "sample1-1", "sample2-1"))
>
>Now I want to add a column to mydata with the experiment ID. The best I 
>could find is that:
>for (i in names(exp)) mydata[mydata[["sample"]] %in% exp[[i]], 
>"experiment"] <- i
>
>In this example, the experiment ID could be extracted from the sample 
>IDs, but this is not the case with my real data so it really is a matter 
>of matching. Of course I also have other columns with my real data.
>
>I'm pretty sure the last line (with the loop) can be improved in terms 
>of readability (speed is not an issue here). I have close to no 
>constraints on 'exp' (here I chose a list, but anything could do), the 
>only thing that cannot change is the format of 'mydata'.
>
>Thank you in advance!
>Ivan
>

-- 
Sent from my phone. Please excuse my brevity.