# [R] Wilcox paired test error message

arun smartpink111 at yahoo.com
Sun Jun 23 22:31:38 CEST 2013

```HI,
May be this helps:
beforesmall aftersmall
63.5      512.0
54.5      237.5
52.5      161.5
78.0      153.5
53.5       68.0
50.5       65.5
69.0       52.0
76.0       59.0
68.0       66.5
75.5       66.5
67.0       45.5
81.0       54.5
49.0       44.0
51.0       42.5
53.0       34.5
wilcox.test(dat1\$beforesmall,dat1\$aftersmall,paired=T)
#
#    Wilcoxon signed rank test with continuity correction
#
#data:  dat1\$beforesmall and dat1\$aftersmall
#V = 55, p-value = 0.7982
#alternative hypothesis: true location shift is not equal to 0
#or
library(reshape2)
dat2<-melt(dat1)
wilcox.test(value~variable,data=dat2,paired=TRUE)
##
#    Wilcoxon signed rank test with continuity correction
#
#data:  value by variable
#V = 55, p-value = 0.7982
#alternative hypothesis: true location shift is not equal to 0

A.K.

Hi,
I've been trying to run a wilcox paired test on some data
beforesmall aftersmall
[1,]        63.5      512.0
[2,]        54.5      237.5
[3,]        52.5      161.5
[4,]        78.0      153.5
[5,]        53.5       68.0
[6,]        50.5       65.5
[7,]        69.0       52.0
[8,]        76.0       59.0
[9,]        68.0       66.5
[10,]        75.5       66.5
[11,]        67.0       45.5
[12,]        81.0       54.5
[13,]        49.0       44.0
[14,]        51.0       42.5
[15,]        53.0       34.5

using
wilcox.test(beforesmall ~ aftersmall,paired=T)
but I get the error message:

Error in wilcox.test.formula(beforesmall ~ aftersmall, paired = T) :
grouping factor must have exactly 2 levels

I don't have any missing values, I have the same amount of data points for
each group and I've looked everywhere trying to find the answer.
Please can somebody tell me how to make it work
thanks

```