CODEWITHSUNDEEP
rdata.table
Orion
Orion

Reputation: 1104

Multi-column condition in a data.table

Let DT be a data.table:

DT <- data.table (col.1 = c(1, 1, 1, 2, 2, 2, 3, 3, 3, 3),
                  col.2 = c(0, 1, 1, 0, 0, 0, 1, 0, 1, 1),
                  #...
                  col.n = c(0, 2, 1, 0, 0, 2, 1, 0, 0, 1),                
                  flag  = 0)

DT
    col.1 col.2 col.n flag
 1:     1     0     0    0
 2:     1     1     2    0
 3:     1     1     1    0
 4:     2     0     0    0
 5:     2     0     0    0
 6:     2     0     2    0
 7:     3     1     1    0
 8:     3     0     0    0
 9:     3     1     0    0
10:     3     1     1    0

How to set flag = T (or 1) where col.1 + col.2 + col.n > 4, without using the column names?

Upvotes: 1

Views: 165

Answers (2)

jeborsel
jeborsel

Reputation: 697

DT[ , flag := fifelse(rowSums(.SD)>4, 1, flag)), .SDcols = !='flag']

Upvotes: 0

akrun
akrun

Reputation: 887118

Another option is to use Reduce

DT[, flag := (Reduce(`+`, .SD)>4)+0L, .SDcols=-'flag'][]

Upvotes: 1

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