Last November I was working on a project for which the client had stated in the spec that all graphs had to be generated using the Google Chart API, which does not scale the graph automatically (or at least it didn't at that time), so I needed to work up something of my own to determine an appropriate range¹ and then map the displayed values into 0-100% of that range.

Which is not necessarily to say that AnonyMonk shouldn't be using one of the many CPAN graphing modules which will handle these details for him (I'm partial to GD::Graph, myself), but it is possible that he may have a legitimate need to do this.

¹ 0-6000 tends to go over better with end users than 3407.21-5296.37, so it's not just a matter of taking your minimum and maximum values as "0" and "100".