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

[Jeff Newmiller]

You have 10^7 columns? That process is bound to be slow.

On April 13, 2018 5:31:32 PM PDT, Jack Arnestad <jackarnestad using gmail.com> wrote:
>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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>
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-- 
Sent from my phone. Please excuse my brevity.