Using for loops in R

Question

I have this line of code that i am using in order to create the table below.

DtTemp <- Dtable[,list("temperature"=paste(temperature,collapse=", ")),by=station.id]

table:

   station.id                  temperature
1:         S1     18, 20.5, 18, 18.6, 21.5
2:         S2 20.1, 18.3, 16.8, 17.5, 16.4
3:         S3   11, 19.1, 18.9, 17.8, 17.6
4:         S4     18, 15.5, 15, 14.9, 15.8

In the table above, temperature values are grouped according to station.id.

I am looking for to create other similar tables, automatically, for every other column in my Dtable dataset. That being said it is obvious that i have more than one station.id values in my original dataset Dtable.

Assuming that a for loop might do it, or something like foreach or iter how should i use them to implement it.?

Is there a way to achieve this, giving at each temperature column, as the example above, the relevant Dtable column name, for which the table is created.?

Appreciate any help.

Answer 1

Yes, you have access to the .SD variable which represents all columns other than the ones involved in grouping, so

Dtable[,lapply(.SD, paste, collapse=", "), by=station.id]

should do the trick