Replace value from other dataframe

Question

I have a data frame (x) with a factor variable which has values seperated by comma. I have another data frame (y) with description for the same values. Now I want to replace the values in the data frame (x) with the description from the data frame (y). Any help would be highly appreciated.

say for example, the two data frame looks like below

data frame (x)
    s.no    x
    1       2,5,45
    2       35,5
    3       45

data fram (y)
s.no    x   description
1       2      a
2       5      b
3       45     c
4       35     d

I need the output as below

s.no    x
1      a,b,c
2      d,b
c       c

Answer 1

With splitstackshape:

library(splitstackshape)

cSplit(x, 'x', ',', 'long')[setDT(y), on='x'][,.(x=paste(description, collapse=',')), s.no]

#   s.no     x
#1:    1 a,b,c
#2:    2   b,d
#3:    3     c