I have the SFS of synonymous sties and non-synonymous sites. It seems more non-synonymous sites are located at low frequency spectrum, which might indicate purifying selection. But how can I test the difference of the two distributions. I noticed some papers using Mann-Whitney U Test. But I am questioning of the application. For example,
x <- c(1,3,5,7,9)
z <- c(9,7,5,3,1)
x and z are clearly different distributions, but the U test gives:
wilcox.test(x,z)
Wilcoxon rank sum test with continuity correction
data: x and z
W = 12.5, p-value = 1
alternative hypothesis: true location shift is not equal to 0
p = 1, no difference! Where is the problem?
Thanks!
Hi! Would Kolmogorov-Smirnov test be helpful? I'm facing the same problem, and wandering if I could know your suggestion about this problem. Thanks a lot!