void
summary_stats (MYSQL_RES *res_set, unsigned int col_num)
{
MYSQL_FIELD		*field;
MYSQL_ROW		row;
unsigned int	n, missing;
double	val, sum, sum_squares, var;

	/* verify data requirements */
	if (mysql_num_fields (res_set) < col_num)
	{
		print_error (NULL, "illegal column number");
		return;
	}
	mysql_field_seek (res_set, 0);
	field = mysql_fetch_field (res_set);
	if (!IS_NUM (field->type))
	{
		print_error (NULL, "column is not numeric");
		return;
	}

	/* calculate summary statistics */

	n = 0;
	missing = 0;
	sum = 0;
	sum_squares = 0;

	mysql_data_seek (res_set, 0);
	while ((row = mysql_fetch_row (res_set)) != NULL)
	{
		if (row[col_num] == NULL)
			missing++;
		else
		{
			n++;
			val = atof (row[col_num]);	/* convert string to number */
			sum += val;
			sum_squares += val * val;
		}
	}
	if (n == 0)
		printf ("No observations\n");
	else
	{
		printf ("Number of observations: %lu\n", n);
		printf ("Missing observations: %lu\n", missing);
		printf ("Sum: %g\n", sum);
		printf ("Mean: %g\n", sum / n);
		printf ("Sum of squares: %g\n", sum_squares);
		var = ((n * sum_squares) - (sum * sum)) / (n * (n - 1));
		printf ("Variance: %g\n", var);
		printf ("Standard deviation: %g\n", sqrt (var));
	}
}