how to get a list of pvalues?

Question

I performed a wilcox test and now I want to extract the p.value in to a list or matrix. ``` DF <- data.frame(A1=sample(1:9, 10, T), A2=sample(1:9, 10, T), A3=sample(1:9, 10, T), B1=sample(1:9, 10, T), B2=sample(1:9, 10, T), B3=sample(1:9, 10, T)) sampA <- DF[,grep('A', names(DF))] # Sample with columns A sampB <- DF[,grep('B', names(DF))] # Sample with columns B lapply(1:nrow(DF), function(i){ wilcox.test(as.numeric(sampA[i,]), as.numeric(sampB[i,]), exact=FALSE ) }) ``` The result of my wilcox test for each rows looks like this: I wanna know how i can get the p.value in a list or a matrix to export to a excel file? [[1]] ``` Wilcoxon rank sum test with continuity correction data: as.numeric(sampA[i, ]) and as.numeric(sampB[i, ]) W = 3, p-value = 0.6579 alternative hypothesis: true location shift is not equal to 0 [[2]] Wilcoxon rank sum test with continuity correction data: as.numeric(sampA[i, ]) and as.numeric(sampB[i, ]) W = 0, p-value = 0.0722 alternative hypothesis: true location…

Accepted Answer

Just add `$p.value` to extract your p.value from your `wilcox.test` object :

```
lapply(1:nrow(DF), function(i){
  wilcox.test(as.numeric(sampA[i,]), as.numeric(sampB[i,]), exact=FALSE )$p.value
}) 
```

Which gives :

```
[[1]]
[1] 1

[[2]]
[1] 1

[[3]]
[1] 0.8247781

[[4]]
[1] 0.8247781
```

By using `sapply` instead of `lapply` you would get a vector instead of a list, which could be easier to manipulate.

```
sapply(1:nrow(DF), function(i){
  wilcox.test(as.numeric(sampA[i,]), as.numeric(sampB[i,]), exact=FALSE )$p.value
})

# [1] 1.0000000 1.0000000 0.8247781 0.8247781 0.0765225 0.8247781 1.0000000
# [8] 0.8247781 0.2682859 0.0765225
```

how to get a list of pvalues?

Solution

Problem