Core Plot: Tick Intervals

Found the solution: Applying a theme changes the painting-behavior of the plot. If I don't apply a theme - everything is fine.

For this is not very intuitive. I would expect that a theme only changes colors or that some aspects can be overridden.

That code should work fine--you'll end up with tick marks and labels at 0, 5, 10, 15, and 20. The settings for visibleRange and gridLinesRange may not be right--leave them at the default of nil to have the axes and grid lines extend the full width and height of the plot area.

If you want to change the number format of the labels, set the labelFormatter to a new NSNumberFormatter object configured to give the number format you want.