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I have the following dataset that I need to display on the heat map:

[30, 15, 66, 7, 9999, 78, 42, 132]

So if I map the values to the color scale using a linear function I only see the spike while the rest of the values I cannot tell apart because the difference between them is insignificant in the scale of that spike.

I tried a log function but it didn't get a good looking picture either.

I don't care about accurate correspondence between the value and the color intensity.

Is there a way to map the values to the color scale so that the difference between all values was visible? Can I mitigate that spike somehow? I am rather asking about established approaches or algorithms addressing problems like this.

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  • $\begingroup$ What language or data visualization tool are you using? $\endgroup$ – Phillip Nordwall Mar 27 '13 at 15:02
  • $\begingroup$ JavaScript and AmMaps controls $\endgroup$ – Trident D'Gao Mar 27 '13 at 15:09
  • $\begingroup$ It doesn't look like you can control the gradient with ammaps but I haven't used it. You could probably filter your data and then do drill down maps to get an overlay effect. $\endgroup$ – Phillip Nordwall Mar 27 '13 at 15:25
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There are many different ways of handling outliers, as well as answers to similar questions here already. I would recommend taking a look at

The first deals with this problem in R. Taking the approach of graphing the non-outliers with a heatmap, then overlaying the outliers and annotating the legend to describe that this is what was done.

The second contains links to general solutions and approaches to outliers.

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