[R] Efficient way to subset rows in R for dataset with 10^7 columns

[Jack Arnestad]

I have a data.table with dimensions 100 by 10^7.

When I do

    trainIndex <-
      caret::createDataPartition(
        df$status,
        p = .9,
        list = FALSE,
        times = 1
      )
    outerTrain <- df[trainIndex]
    outerTest  <- df[-trainIndex]

Subsetting the rows of df takes over 20 minutes.

What is the best way to efficiently subset this?

Thanks!

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