calculate_age_from_dob
                        Function to calculate age from date of birth
calculate_age_from_year
                        Function to calculate age from year of birth
check_colno_pattern_colname
                        ###############################################################################
                        Function to return the column number if a given
                        pattern is contained in the column names of a
                        data
check_column_exists     Function to check the given column exists
check_load_packages     Function to check the package is installed, if
                        not install
cohensd                 Function to find the effect size Cohen's d
convert_date_numeric_stdform
                        Helper function to keep date formats in
                        year-month-date
convert_date_numeric_stdform_old
                        Helper function to keep date formats in
                        year-month-date
convert_date_string_stdform
                        Helper function to keep date formats in
                        year-month-date
convert_to_number       Function that convert a number represented as
                        character array
descriptive_stats_col   Function to return descriptive statistics, sum,
                        no of observations, mean, mode. median, range,
                        standard deviation and standard error
get_colno_pattern_colname
                        Function to return the column number if a given
                        pattern is contained in the column names of a
                        data
get_columnno_fornames   Function to return the column number for column
                        name
get_contents_cols       Function to return the unique contents of the
                        column given the column name
get_mode_from_vector    ###############################################################################
                        Function to return mode
get_sem                 ###############################################################################
                        Function to estimate standard error of the mean
present_mean_sd_rmna_text
                        ###############################################################################
                        Function to present the mean and sd of a data
                        set in the form Mean (SD)
represent_categorical_data
                        Function to find the number and percentages of
                        categories
represent_categorical_textdata
                        Function to represent categorical data in the
                        form - numbers (percentage)
return_subgroup_omitna
                        Function to return a subgroup when certain
                        variable equals the given value while omitting
                        those with NA
test_age                Function to check the format of 'age' in data
test_column_contents    Function to check the format of column contents
test_columnnames        Function to test column names of a data being
                        different from what specified
test_data_numeric       Function to check the format of a numeric
                        column
test_data_numeric_norange
                        Function to check the format of a numeric
                        column when the values are not bounded
test_data_string        Function to check the format of a string column
test_data_string_restriction
                        Function to check the format of a string column
                        when the string values are given
test_file_exist_read    Function to throw error on invalid directory or
                        file and if not readable
test_gender             Function to check the format of 'gender' column
                        in data
