Algorithm for “nice” grid line intervals on a graph

Question

I need a reasonably smart algorithm to come up with \"nice\" grid lines for a graph (chart).

For example, assume a bar chart with values of 10, 30, 72 and 60. You k

Answer 1

Another idea is to have the range of the axis be the range of the values, but put the tick marks at the appropriate position.. i.e. for 7 to 22 do:

[- - - | - - - - | - - - - | - - ]
       10        15        20

As for selecting the tick spacing, I would suggest any number of the form 10^x * i / n, where i < n, and 0 < n < 10. Generate this list, and sort them, and you can find the largest number smaller than value_per_division (as in adam_liss) using a binary search.