CODEWITHSUNDEEP
rloopsdata.table
IVIM
IVIM

Reputation: 2367

Accessing by variable column name in data.table - Error: `cannot change value of locked binding for '.SD'`

This is related to my earlier question on convenience of data.table for loops and functions: How to use data.table within functions and loops? and related post: Data.table meta-programming.
This little code shows how conveniently this is done with data.table it is (e.g. compare to dplyr).

At first, I got cannot change value of locked binding for '.SD' error when I use get(strY) or .SD / .SDcols=colY below. But when I restarted the R Session, it all worked.

dt <- data.table(ggplot2::diamonds)
nY <- 1;                       nX <- c(5:7)
strY <- names(dt)[nY];         strX <- names(dt)[nX];        

dt[,strY, with=F] # OK
dt[,nY, with=F] # OK

dt[,get(strY)] # OK NOW: 
#NO MORE: Error in assign(ii, SDenv$.SDall[[ii]], SDenv) : 
#   cannot change value of locked binding for '.SD'
dt[, .SD, .SDcols=strX] # OK NOW: 
#NO MORE Error in assign(ii, SDenv$.SDall[[ii]], SDenv) : 
#   cannot change value of locked binding for '.SD'

Upvotes: 1

Views: 1974

Answers (1)

IVIM
IVIM

Reputation: 2367

This problem was resolved somehow by restarting the R session. - All lines work. This code has become the key work-stone for all my loop/function needs. Thanks to reviewers!

Upvotes: 5

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