Unable to use a character array as a grouping variable. First convert the character array to a cell array of character vectors using cellstr. Then specify the cell array as a grouping variable. A grouping variable must be a vector. A grouping variable of class ''{0}'' is not supported. All grouping variables must have the same size. Unable to group rows using unique values of the input variables. UNIQUE returned an error. Unable to group rows using unique values of the input variables. The value returned by the UNIQUE method had the wrong number of rows.