CODEWITHSUNDEEP
rdata.table
Henk
Henk

Reputation: 3656

Apply a column wise function in a list of data.tables

I have read a folder with Excel files with a lapply function and now have a list with data.tables. The individual data.tables have different dimensions and column names.

Now I have to apply a series of functions on this list to clean it up. Where I get stuck is: how do I apply a column-wise function on every data.table inside this list? 

library(data.table)

# make a list of data.tables
set.seed(123)
dt = data.table(x = runif(10), y = runif(10))
dt2 = data.table(a = runif(10), y = runif(10), z = runif(10))

l = list(dt, dt2)
names(l) = c("dt", "dt2")

# sample function to be applied
func = function(x) {
  y = x * 2
}

# how it would work for an invidual data.table
dt[, lapply(.SD, func)]

Upvotes: 3

Views: 1131

Answers (1)

akrun
akrun

Reputation: 887951

We loop through the list with lapply and apply the function column wise within each list element.

lapply(l, function(x) x[,lapply(.SD, func)])

Upvotes: 5

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