I am trying to use MLSeq classify() function in R, and I always got an error message:

Error in relevel.factor(conditions, which(levels(conditions) == ref)) : 
  'ref' must be of length one

However my code looks consistent, ref = "c" should be length of one, also tried to set reference level in the factor, nothing worked so far. I think the problem in the model, where I use

~ treatment * hour, so MLSeq wants to use recreated factors, which I cannot figure out.

treatment is a factor with c and t (control, treated) hour is a vector with hours after treatment.

Anyone has an idea how to solve this? Thanks in advance.