update column value of data.table in R based on another column values

Question

library(data.table)

train <- fread(input = "../train.csv", header = TRUE, sep = ",", 
           stringsAsFactors = FALSE, data.table = TRUE)

train$Response <- "" #create new column with values ""
train$Response <- paste(train[, 15:20, with = FALSE], collapse = "")

RStudio console:
> is.data.frame(train)
[1] TRUE
> is.data.table(train)
[1] TRUE

Columns with indexes from 15 to 20 has values = 1 or 0 of int type.

I have tryied to make one column "response" (character type) with values "0101..." as result of concatenation values 1 and 0 of columns, described above.

After this procedure I see abnormal behaviour of R studio, can't access to train etc.

Maybe something wrong?

This doesn't make a lot of sense at the moment (since data.tables don't naturally use the "$"-operator). If train is a data.table then you should edit your question to construct an example that creates an object similar to your use case. — IRTFM
– IRTFM, Commented Nov 21, 2016 at 2:51

akrun · Accepted Answer · 2016-11-21 04:19:37Z

1

We can specify the columns to paste in .SDcols, use paste0 with do.call on the Subset of Data.table (.SD), and assign (:=) to create the 'Response' column.

train[, Response := do.call(paste0, .SD), .SDcols = 15:20]

answered Nov 21, 2016 at 4:19

akrun

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