Making a character string with column names with zero values

Question

The 4th column is my desired column. Video,Webinar,Meeting,Conference are the 4 type of activities that the different customers(names) can engage in. You can see,in a given row,

Answer 1

A possible solution:

DT[, nextstep := paste0(names(.SD)[.SD==0], collapse = ','), 1:nrow(DT), .SDcols = 2:5][]

which gives:

   Name Video Webinar Meeting Conference                   nextstep
1: John     1       0       0          0 Webinar,Meeting,Conference
2: John     1       1       0          0         Meeting,Conference
3: John     1       1       1          0                 Conference
4:  Tom     0       0       1          0   Video,Webinar,Conference
5:  Tom     0       0       1          1              Video,Webinar
6: Kyle     0       0       0          1      Video,Webinar,Meeting

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When you want to order the names as you specified in the comments, you can do:

lvls <- c('Webinar', 'Meeting', 'Conference', 'Video')
DT[, nextstep := paste0(lvls[lvls %in% names(.SD)[.SD==0]], collapse = ','), 
   1:nrow(DT), .SDcols = 2:5][]

which gives:

   Name Video Webinar Meeting Conference                   nextstep
1: John     1       0       0          0 Webinar,Meeting,Conference
2: John     1       1       0          0         Meeting,Conference
3: John     1       1       1          0                 Conference
4:  Tom     0       0       1          0   Webinar,Conference,Video
5:  Tom     0       0       1          1              Webinar,Video
6: Kyle     0       0       0          1      Webinar,Meeting,Video

Instead of using paste0 (with collapse = ',') you can also use toString.

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Used data:

DT <- fread('Name     Video   Webinar  Meeting  Conference
             John       1         0        0        0
             John       1         1        0        0
             John       1         1        1        0
             Tom        0         0        1        0
             Tom        0         0        1        1
             Kyle       0         0        0        1')