public static Column var(DataRowsFacade dataFrame, String columnName) {
        return dataFrame.get().groupBy(columnName).agg(functions.variance(columnName)).col(columnName);
    }
public static Column var ( DataRowsFacade dataFrame , String columnName ) { return dataFrame . get ( ) . groupBy ( columnName ) . agg ( functions . variance ( columnName ) ) . col ( columnName ) ; }
Standard deviation for a column

@param dataFrame  the dataframe to
get the column from
@param columnName the name of the column to get the standard
deviation for
@return the column that represents the standard deviation