Uploading a source file with raw data and one source factor

[StefanoUniBz]

Hello I am trying to run MixSiar by considering raw source data, using the values of end-members as date-specific. Accordingly, i ensured that both the source and the mixture files had a column called "Date" and used this variable when loading the source data, by setting [...] source_factors="Date" [...]. Every date has a value for the mixture and at least one value for each end-member. Unfortunately, i encounter the following error message when loading the source data:

Error in list.sources.bylev[[lev]] <- SOURCE[SOURCE[, source_factors] == : attempt to select less than one element in integerOneIndex

I tried to change the format of the date by considering the variable day of the year, and changing numbers into letters, but the problem still persists...do you have some suggestions to solve this issue?