Match a string within column values having multiple values

Question

Please help me with this I have a data table as below

    dt2 <- data.table(ID = c(1,1,2,2,3,3,4,4,4), variable =     c("a","b","a","c","c","d","e","b","a"))
    dt3 <- dt2[, list(variables = paste(variable, collapse = " | ")), by = ID]
    dt3[,chk:=sample(letters[1:2])]
    dt3
    ID variables chk
1:  1     a | b   b
2:  2     a | c   a
3:  3     c | d   b
4:  4 e | b | a   a

I want to filter records where variables contain chk. In the example above row 3 should be removed.

Pierre L · Accepted Answer · 2015-11-24 13:06:20Z

4

Here's an mapply approach. It takes the two parameters element by element in the operation:

dt3[mapply(grepl, x=variables, chk)]
#   ID variables chk
#1:  1     a | b   b
#2:  2     a | c   a
#3:  4 e | b | a   a

answered Nov 24, 2015 at 13:06

Pierre L

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David Arenburg · Accepted Answer · 2015-11-24 13:33:09Z

1

We can use paste with grep

dt3[with(dt3, grep(paste(chk, collapse='|'), variables)),]
#     ID variables chk
#1:  1     a | b   a
#2:  2     a | c   b
#3:  4 e | b | a   b

edited Nov 24, 2015 at 13:33

David Arenburg

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answered Nov 24, 2015 at 13:31

akrun

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