Allow number formatting of chart axis

A calculated value such as 'week number' can be created through report formulas. In a list report, I can format that number to display without a decimal. When that week number is shown as x-axis on a bar chart, however, it always contains a decimal. Casting the value to a string will remove the decimal but throws off the sort as 1, 11, 12 will then show up ahead of 2, 3, 4.