Home/ Questions/Q 8762509
In Process

The Archive Base Latest Questions

Editorial Team
  • 0
Asked: 2026-06-13T15:32:54+00:00

I have a huge list with data.frames (same number of columns, different number of

  • 0

I have a huge list with data.frames (same number of columns, different number of rows).
I succeeded to use apply – instead of the for loops I learned to avoid – to create a mean value over specific columns in each list element with 

t2<-lapply(t1, function(x) cbind(x,rowMeans(x[,c("ColumnX","ColumnY","ColumnZ")])))

The problem I am stuck with now is the new columns name. It is “rowMeans(x[,c(“ColumnX”,”ColumnY”,”ColumnZ”)])”.

How can I change this for all list elements? My poor “lapply”-knowledge was not sufficient for this task.

Share

Leave an answer

You must login to add an answer.

Need An Account,

1 Answer

  1. Editorial Team

    There’s two ways to do this, and it actually has to do with the cbind function and not the lapply function:

    cbind(x,DesiredName = rowMeans(x[,...]))

    Or after you’ve cbind’ed:

    > names(x)
[1] "Column X" "Column Y" "Column Z" "rowMeans(x[,...])"
> names(x)[4]
"rowMeans(x[,...])"
> names(x)[4] <- "DesiredName" ###Assign a name to the fourth column
> names(x)
[1] "Column X" "Column Y" "Column Z" "DesiredName"

    That’s obviously the long way, but it useful for if you forget to name something during the apply or cbind process.

    • 0