Paste multiple columns together

Question

I have a bunch of columns in a dataframe which I want to paste together (seperated by "-") as follows:

data <- data.frame('a' = 1:3,                     'b' = c('a','b','c'),                     'c' = c('d', 'e', 'f'),                     'd' = c('g', 'h', 'i')) i.e.           a   b   c  d        1   a   d   g        2   b   e   h        3   c   f   i   

Which I want to become:

a x   1 a-d-g   2 b-e-h   3 c-f-i   

I could normally do this with:

within(data, x <- paste(b,c,d,sep='-')) 

and then removing the old columns, but unfortunately I do not know the names of the columns specifically, only a collective name for all of the columns, e.g. I would know that cols <- c('b','c','d')

Does anyone know a way of doing this?

Answer 1

# your starting data.. data <- data.frame('a' = 1:3, 'b' = c('a','b','c'), 'c' = c('d', 'e', 'f'), 'd' = c('g', 'h', 'i'))   # columns to paste together cols <- c( 'b' , 'c' , 'd' )  # create a new column `x` with the three columns collapsed together data$x <- apply( data[ , cols ] , 1 , paste , collapse = "-" )  # remove the unnecessary columns data <- data[ , !( names( data ) %in% cols ) ] 

Answer 2

As a variant on baptiste's answer, with data defined as you have and the columns that you want to put together defined in cols

cols <- c("b", "c", "d") 

You can add the new column to data and delete the old ones with

data$x <- do.call(paste, c(data[cols], sep="-")) for (co in cols) data[co] <- NULL 

which gives

> data   a     x 1 1 a-d-g 2 2 b-e-h 3 3 c-f-i