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

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