problem with FST script

[vincenzolandi]

Dear Dr. Giannico, thank you to submitting the script...I am running it but i get an error:
Error in if (popelem[1] == popelem[2]) { :
missing value where TRUE/FALSE needed

ehan I execute these lines..

pairwise population matrix FST calculation

for(i in poplevels) {
for(j in poplevels) {
popelem= unlist(strsplit(res[i,j],"/"))

#takes selection of samples an population to use for each pair
flag<- pop_code %in% c(popelem[1],popelem[2])
samp.sel<- sample.id[flag]
pop.sel<- pop_code[flag]

if (popelem[1]==popelem[2]){result="0"}else{
  result = snpgdsFst(genofile, sample.id=samp.sel, population=as.factor(pop.sel), 
                     autosome.only=FALSE, method="W&C84")
}
res[i,j]=as.character(result)

}
}

thank you in advance for help