Hi

I want to run following linear mixed model, for each metabolite in my dataset where I hace fixed effects gender and timepoint, and random effect the person_id.

For each metabolite seperately, the code works, but if I put it in this for loop, it gives following error:

Error in model.frame.default(data = sample_df_M, drop.unused.levels = TRUE,  : 
  variable lengths differ (found for 'gender')

Is there another way ? Because the code does work if i use the first metabolite, which is Valine (Val) , then I get the output. As soon as I put it in the for loop, it gives the error.

library("lme4")
metabolites <- colnames(metab.matrix)
for (m in metabolites) {
  out <- lmer(m ~ gender+ month+ (1|person_id), data=sample_df_M)
  out0 <- lmer(m ~ (1|person_id), data = sample_df_M)
  comp <- anova(out0, out)
  pv <- comp[["Pr(>Chisq)"]][[2]]
  print(pv)
}

thank you in advance!