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I would like to store the Group information of the data.table below (DT1) as a label for the column names of a second data.table. The column names of the second data.table (DT2) are identical to the nr information of the first data.table.

set.seed(1)
    DT1 <- data.table(nr= paste0('x',1:100),Group = c(rep("A",10),rep("B",10),rep("C",10),rep("D",10),rep("E",10),rep("F",10),rep("G",10),rep("H",10),rep("I",10),rep("J",10)),
                          id = c(rep(1,20),rep(2,20),rep(3,20),rep(4,20),rep(5,20)),
                          Time = rep(seq(as.Date("2010-01-03"), length=20, by="1 month") - 1,5),
                          norm = round(runif(100)/10,2),
                          y = sample(100,100),
                          x2 = round(rnorm(100,0.75,0.3),2),
                          x3 = round(rnorm(100,0.75,0.3),2),
                          x4 = round(rnorm(100,0.75,0.3),2),
                          x5 = round(rnorm(100,0.75,0.3),2))
    DT2 <- data.table(matrix(0, ncol=100, nrow=2, dimnames=list(NULL, 
                 paste0('x',1:100))))

I have previously done something like this:

library(Hmisc)
for (i in seq_len(ncol(DT2))) {Hmisc::label(IV[[DT1$`nr`[i]]]) <- ES1obs$Group[i]}

But this has a lot of problems when the amount of columns are not identical.

How can I write the code so that it will compare the nr column of DT1 with the column names of DT2, and add the Group column when they are a match?

Desired outcome:

label(DT2$x1) <- "A"
label(DT2$x2) <- "A"
...
label(DT2$x100) <- "J"
Tom
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1 Answers1

1

Try using match assuming all the column names of DT2 are always present in DT1$nr

library(Hmisc)

for (i in seq_len(ncol(DT2))) { 
    label(DT2[[i]]) <-  DT1$Group[match(names(DT2)[i], DT1$nr)] 
 }

head(label(DT2))
# x1  x2  x3  x4  x5  x6 
#"A" "A" "A" "A" "A" "A" 

tail(label(DT2))
# x95  x96  x97  x98  x99 x100 
# "J"  "J"  "J"  "J"  "J"  "J"
Ronak Shah
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