# Re: [R] Running wilcox.test function on two lists

From: Dimitrios Rizopoulos <Dimitris.Rizopoulos_at_med.kuleuven.be>
Date: Thu 07 Sep 2006 - 20:11:39 GMT

try something like the following:

lis1 <- c(lapply(1:10, rnorm, n = 10))
lis2 <- c(lapply(1:10, rnorm, n = 10))
lis1[[5]] <- lis2[[8]] <- numeric(0)

```############################################
```
ind <- sapply(lis1, length) > 0 & sapply(lis2, length) > 0 lis1 <- lis1[ind]
lis2 <- lis2[ind]

mapply(function(x, y) wilcox.test(x, y)\$p.value, lis1, lis2)

I hope it helps.

Best,
Dimitris

Dimitris Rizopoulos
Ph.D. Student
Biostatistical Centre
School of Public Health
Catholic University of Leuven

```Tel: +32/(0)16/336899
Fax: +32/(0)16/337015
Web: http://med.kuleuven.be/biostat/
http://www.student.kuleuven.be/~m0390867/dimitris.htm

```

Quoting "Raj, Towfique" <trajnp@gmail.com>:

> Dear all,
> I'm a newbie to R and I would really apperciate any help with the following:
>
> I have two lists, l1 and l2:
>
> l1:
> \$"A*0101"
> [1] 0.076 0.109 0.155 0.077 0.09 0 0 0.073
> [9] 0.33 0.0034 0.0053
>
>
> \$"A*0247"
> [1] 0 0 0.5 .004 0 0 0
>
> \$"A*0248"
> [1] 0 0 0.3 0 0.06
>
> ....
>
> l2:
>
> \$"A*1101"
> [1] 0.17 0.24 0.097 0.075 0.067
>
> \$"A*0247"
> numeric(0)
>
> \$"A*0248"
> [1] 0.031
>
> ....
>
> Basically, what I want to do is run wilcox.test() on each entry pair
> in the list.
>
> 1) I want to loop through the list to run wilcox.test for each entry
> of the list. How would I do that? mapply()?
>
> wilcox.test(l0[[1]],l1[[1]]) for the first one and so on....
>
> 2) I want to exclude the list entry which has no values (i.e. A*0247).
>
> 3) Finally, I only want the to see the 'p-value' for each list names.
> The output I want capture is only the 'p-value' object from
> wilcox.test.
>
> name p-value
> A*0101 0.8329
> .... ....
>
> I'm grateful for any help, or any pointers to a good online tutorial.
>
> Thanks a lot in advance,
>
> -T.
>
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