I have a file with data arranged in the following way:


0.051 0.056 0.269639

0.051 0.057 0.252626

0.051 0.058 0.23856


I'd like to plot an heat map and I've managed something like this:

ListDensityPlot[  Import["\HeatMap.txt", "Data"],   PlotRange -> All, ColorFunction -> Hue]

Wich gives me:

Heat Map

The problem is that I don't know what the colors are corresponding to in terms of values. Can I mark colors for specific value ranges? Or how can I find out how the color gradient is comparing to the values?

Also, there is a particular point of interest in the data, how can I show it?

  • 1
    $\begingroup$ "colors for specific value ranges" - why not use Blend[]? "find out how the color gradient is comparing to the values" - that's what legends are for, no? $\endgroup$ Commented Aug 6, 2016 at 11:04
  • $\begingroup$ Of course, I just wasn't aware how to add them. Thank you. $\endgroup$
    – phytab
    Commented Aug 6, 2016 at 15:36

1 Answer 1

ListDensityPlot[{{1, 1, 1, 1}, {1, 2, 1, 2}, {1, 1, 3, 1}, {1, 2, 1, 
   4}}, PlotLegends -> Automatic, 
 ColorFunction -> (Blend[{Yellow, Red}, #] &)]

Generates labels where the values in the plot range between Yellow and Red.

You can check the colour for the scale:

Blend[{Yellow, Red}, 0.5]

For instance gives the colour for the median value. enter image description here

This epilogue finds the lowest value, (which in this case is of course not unique, but I needed an easy dataset)

data = Table[
   With[{r = RandomReal[{0, 5}], 
     t = RandomReal[{0, 2 Pi}]}, {r Cos[t], r Sin[t], 
     Sin[r^2]/r^2}], {10^4}];
ListDensityPlot[data, PlotRange -> All, 
 ColorFunction -> (Blend[{Yellow, Red}, #] &), 
 Epilog -> {Black, PointSize -> 0.01, 
 Point[Flatten[MinimalBy[data, Last]][[1 ;; 2]]]}]

enter image description here

  • $\begingroup$ Do you know how I can mark specific point? $\endgroup$
    – phytab
    Commented Aug 6, 2016 at 15:39
  • $\begingroup$ @phytab I'm not sure I understand what you mean. $\endgroup$
    – Feyre
    Commented Aug 6, 2016 at 15:43
  • $\begingroup$ In your picture, let's say I wanted to mark the point (2.0,2.0) with a black dot. How could I do that? Or have it always mark the (x,y) that gives the lowest z for example. $\endgroup$
    – phytab
    Commented Aug 6, 2016 at 15:56
  • $\begingroup$ @phytab You could do something like {Black, Yellow, Yellow, Orange, Orange, Red, Red}, or say {Yellow, Yellow, Black, Orange, Orange, Red, Red} to have a small band at $3/7\pm 1/14$ at the range of values be black. $\endgroup$
    – Feyre
    Commented Aug 6, 2016 at 16:07
  • 1
    $\begingroup$ @phytab Ok, and here I had just finished my example :), I'll add it anyway. $\endgroup$
    – Feyre
    Commented Aug 6, 2016 at 16:27

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