2

I have a colour scale, used as a legend for a choropleth, that looks like this:

enter image description here

The legend represents distance from the mean.

However, the ends of the scale are not clamped - the uppermost range may include values that are greater than x2, and the lowest range may include values less that x0.1.

What is the correct way to display this the the user? I've had multiple attempts, but feel that the outcome is lacking and my testers have found each to be misleading.

Things I've tried:

<x0.1 ... x2<
-x0.1 ... x2+
-100% ... +100%

Thanks!

  • In the bands that aren't on the end, are all values the same? (Meaning, is everything in the x0.75 band exactly x0.75? Or is there actually a range of values?) – Graham Herrli Aug 15 '14 at 13:55
  • @3nafish It's a quantized scale, so although the values are continuous, the colours on the map are always discrete. Essentially the numbers are rounded to the nearest band. – Jivings Aug 15 '14 at 14:03
  • 1
    In that case, I have an answer for you. – Graham Herrli Aug 15 '14 at 14:06
2

Label the areas between the bands rather than the bands themselves.

enter image description here

If you know your minimum and maximum values, you could also add those at the very end of the legend.

enter image description here

This way, it's clear what range of values each band represents rather than just pretending that everything in the range equals the value it has been quantized to.


EDIT: If it's important to show clearly when values are very close to the middle, you could add an additional band in the middle with values close to x1.

enter image description here

  • Currently areas that are about average appear as the colour that is labeled x1 (the lightest blue). Don't you think that your suggestion brings ambiguity to the bands? What colour would dead on average now be? – Jivings Aug 15 '14 at 14:09
  • @Jivings, if it's important to emphasize when values are nearly unchanged, you could always just add another band in the middle. (I've edited my post to show this.) – Graham Herrli Aug 15 '14 at 14:19
  • I'm unsure about this, but I'll run it past the users. Thanks! – Jivings Aug 15 '14 at 14:43

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