Perform Student's t-test between data.frames contained in two lists

Question

I have got two separate lists which contain 4 data.frames each one. I need to perform a Student's t-test (t.test) for rainfall between each data.frames within the two lists.

Here the lists:

lst1 = list(data.frame(rnorm(20), rnorm(20)), data.frame(rnorm(25), rnorm(25)), data.frame(rnorm(16), rnorm(16)), data.frame(rnorm(34), rnorm(34)))    
lst1 = lapply(lst1, setNames, c('rainfall', 'snow'))

lst2 = list(data.frame(rnorm(19), rnorm(19)), data.frame(rnorm(38), rnorm(38)), data.frame(rnorm(22), rnorm(22)), data.frame(rnorm(59), rnorm(59)))
lst2 = lapply(lst2, setNames, c('rainfall', 'snow'))

What I would need to do is:

t.test(lst1[[1]]$rainfall, lst2[[1]]$rainfall)
t.test(lst1[[2]]$rainfall, lst2[[2]]$rainfall)
t.test(lst1[[3]]$rainfall, lst2[[3]]$rainfall)
t.test(lst1[[4]]$rainfall, lst2[[4]]$rainfall)

I can do it as above by writing each of the 4 data.frames (I actually have 40 with my real data) but I would like to know if there exists a smarter and quickier way to do it.

Here below what I tried (without success):

myfunction = function(x,y) {
  test = t.test(x, y)
  return(test)
}

result = mapply(myfunction, x=lst1, y=lst2)

Please provide a reproducible sample for people to work with. — lmo, Feb 11 '17 at 22:51
When I run the code with your sample data it gives back t-test results using your `mapply()` line. What is your error and what is your expected result? — Tonio Liebrand, Feb 11 '17 at 23:12

score 1 · Answer 1 · answered Feb 11 '17 at 23:56

1

x <- NULL
for (i in seq_along(lst1)){
  x[[i]] <- t.test(lst1[[i]]$rainfall, lst2[[i]]$rainfall)
}
x

answered Feb 11 '17 at 23:56

lizzie

606
6
15

When giving an answer it is preferable to give [some explanation as to WHY your answer](http://stackoverflow.com/help/how-to-answer) is the one. – Stephen Rauch Feb 12 '17 at 01:16

score 0 · Accepted Answer · answered Feb 11 '17 at 22:54

0

Works for me. I would use simplify = FALSE to get the results formatted better though.

lst1 <- list()
lst1[[1]] <- data.frame(rainfall = rnorm(10))
lst1[[2]] <- data.frame(rainfall = rnorm(10))
lst2 <- list()
lst2[[1]] <- data.frame(rainfall = rnorm(10))
lst2[[2]] <- data.frame(rainfall = rnorm(10))

myfunction = function(x,y) {
  test = t.test(x$rainfall, y$rainfall)
  return(test)
}

mapply(myfunction, x = lst1, y = lst2, SIMPLIFY = FALSE)

answered Feb 11 '17 at 22:54

Tonio Liebrand

17,189
4
39
59

the data.frames contains diverse number of observations, see my example. thanks – aaaaa Feb 11 '17 at 23:08

Perform Student's t-test between data.frames contained in two lists

2 Answers2