Efficiently perform row-wise distribution test

Question

I have a matrix in which each row is a sample from a distribution. I want to do a rolling comparison of the distributions using ks.test and save the test statis

Answer 1

Here's a dplyr solution that gets the same result as your loop. I have my doubts if this is actually faster than the loop, but perhaps it can serve as a first step towards a solution.

require(dplyr)
mt %>% 
  as.data.frame %>%
  mutate_each(funs(lag)) %>%
  cbind(mt) %>%
  slice(-1) %>%
  rowwise %>%
  do({
    x = unlist(.)
    n <- length(x)
    data.frame(ks = ks.test(head(x, n/2), tail(x, n/2))$statistic)
  }) %>%
  unlist %>%
  c(NA, .) %>%
  matrix