Factor covariates can give trouble in multi-session models if the levels differ among sessions. A warning is provided by verify.capthist. This function forces factor covariates to use the same levels.
shareFactorLevels(object, columns = NULL, stringsAsFactors = TRUE)
An object of the same class as input. A single-session object is passed unchanged except for possible conversion of character values to factor (stringsAsFactors = TRUE).
multi-session capthist object or list of traps or mask objects
indices of columns to fix (default all)
logical; if TRUE then character columns are converted to factor
Factor-valued covariates are coerced to use the same set of levels for each session of a multi-session capthist object or each component of a list of traps or masks. The combined level set is the union of all levels in separate sessions. The order of levels follows the default in factor (alphabetical according to current locale).
Setting stringsAsFactors = TRUE causes character-valued columns to be converted to factors.
verify.capthist