Paste multiple columns together

# 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 ) ]

Using tidyr package, this can be easily handled in 1 function call.

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

tidyr::unite_(data, paste(colnames(data)[-1], collapse="_"), colnames(data)[-1])

  a b_c_d
1 1 a_d_g
2 2 b_e_h
3 3 c_f_i

---

Edit: Exclude first column, everything else gets pasted.

# tidyr_0.6.3

unite(data, newCol, -a) 
# or by column index unite(data, newCol, -1)

#   a newCol
# 1 1  a_d_g
# 2 2  b_e_h
# 3 3  c_f_i

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