mlogit

I am trying to add the fitted values of my multinomial logistic regression to the original data frame (called "ORDERS"). Unfortunately this is not possible, as apparently the predicted probabilities and the data frame don't have the same length - even though I use na.exclude in the regression. Maybe this has something to do with the necessary mlogit.data transformation, so that na.exclude does not work? mlModel_refPRE_STD <- mlogit(PAYMENT_METHOD ~ 1 | GROSS_RETAIL_TOTAL_STD + SOLVENCY_SCORE_STD + GENDER + EXISTING_CUSTOMER, data=mlORDERS, reflevel="PRE", na.action=na.exclude) > ORDERS

I discovered the mlogit - package for multinomial logit models in search of estimating a multinomial mixed logit model. After reading the excellent vignette I discovered that I could not apply my data on any of the described examples. I now write in hope of help with my problem and created a minimal example to illustrate my situation. The Problem is as follows: There are words with the consonant 'Q' somewhere. Now an experiment was conducted with people who were tasked to listen to these words and say if they heard a Q, an U or some OTHER consonant. This has to modeled in dependence of some