Scale-scheme misses a color

[IsaacNoel]

The palette:scale-scheme primitive incorrectly scales its value to a color. This bug is present in the library model Palette Example.

In the model, this code:

to normal-scale-scheme
  ask patches [
    set plabel round patch-value
    set pcolor palette:scale-scheme "Sequential" "Reds" 9 patch-value 0 10
  ]
end

where patch-value is calculated as:

to-report patch-value
  let normalized-value (pxcor + (pycor * world-width)) / (world-width * world-height)
  report normalized-value * 10 + 5
end

creates the following view:
.

There should be 9 colors in the view because palette:scale-scheme will report one of 9 colors from "Sequential" "Reds" 9, depending on how 'patch-value' scales from 0 to 10. However, the view only shows 8 colors.

Here's another example of the bug. The command:

ask patches [set pcolor palette:scale-scheme "Divergent" "BrBG" 3 pxcor min-pxcor max-pxcor]

creates the following view:

which should have 3 evenly spaced colors.

There must be something wrong with how the number is scaled to a color.

[brandesNW]

Fixed by PR #12