How to apply a shapiro test by groups in R?

Question

I have a dataframe where all my 90 variables have integer data, of the type:

code | variable1 | variable2 | variable3 | ...

AB | 2 | 3 | 10 |

Answer 1

Using mtcars data from R

mydata<-mtcars
 kk<-Map(function(x)cbind(shapiro.test(x)$statistic,shapiro.test(x)$p.value),mydata)
library(plyr)
myout<-ldply(kk)
names(myout)<-c("var","W","p.value")
myout
    var         W      p.value
1   mpg 0.9475648 1.228816e-01
2   cyl 0.7533102 6.058378e-06
3  disp 0.9200127 2.080660e-02
4    hp 0.9334191 4.880736e-02
5  drat 0.9458838 1.100604e-01
6    wt 0.9432578 9.265551e-02
7  qsec 0.9732511 5.935208e-01
8    vs 0.6322636 9.737384e-08
9    am 0.6250744 7.836356e-08
10 gear 0.7727857 1.306847e-05
11 carb 0.8510972 4.382401e-04