Skip to main content

plotting - ListPlot coloring by density of points


I have a set of points on a circumference:


points = Map[Normalize, RandomReal[{-1, 1}, {3000, 2}]]

And I want to plot them and color the plot according to the density of points. You see, ListPlot[points] will just give me that, a simple plot, on which I can't see the distribution of the points on the circle.



Maybe there is an option?


I hope you guys can understand what I'm asking.


Edit/Follow-up


I used SmoothDensityHistogram[points, ColorFunction -> "Rainbow"]


This is what it looks like


Now, it's not really what I'm looking for. I kind of wanted it to look like the original plot, just the circumference.



Answer



Here is what I think you wanted:


points = Map[Normalize, RandomReal[{-1, 1}, {3000, 2}]];


d = SmoothKernelDistribution[points];

colors = Hue /@ Rescale[PDF[d, #] & /@ points];

Graphics[Transpose[{colors, Point /@ points}]]

pic


Here the SmoothKernelDistribution is evaluated in the plane, giving you a two-dimensional interpretation of density. One could also understand your question as asking for a one-dimensional density of points only on the circle. But I followed the simplest interpretation here.


For completeness, here is an implementation using ListPlot. The colors are contained in PlotStyle, but in order to make them apply to each point individually I have to add another level of depth to the list points:


ListPlot[Map[List, points], PlotStyle -> colors, 

AspectRatio -> Automatic]

listPlot


I may as well add the treatment of the density as purely one-dimensional on the circle: here I convert the elements of points to their polar angle coordinate, and then calculate the density in this polar angle:


arc = ArcTan /@ points;

d = SmoothKernelDistribution[arc];

colors = Hue /@ Rescale[PDF[d, #] & /@ arc];


Then proceed with the plots as above. One can of course play more with the options of SmoothKernelDistribution, depending on your application.


Comments

Popular posts from this blog

front end - keyboard shortcut to invoke Insert new matrix

I frequently need to type in some matrices, and the menu command Insert > Table/Matrix > New... allows matrices with lines drawn between columns and rows, which is very helpful. I would like to make a keyboard shortcut for it, but cannot find the relevant frontend token command (4209405) for it. Since the FullForm[] and InputForm[] of matrices with lines drawn between rows and columns is the same as those without lines, it's hard to do this via 3rd party system-wide text expanders (e.g. autohotkey or atext on mac). How does one assign a keyboard shortcut for the menu item Insert > Table/Matrix > New... , preferably using only mathematica? Thanks! Answer In the MenuSetup.tr (for linux located in the $InstallationDirectory/SystemFiles/FrontEnd/TextResources/X/ directory), I changed the line MenuItem["&New...", "CreateGridBoxDialog"] to read MenuItem["&New...", "CreateGridBoxDialog", MenuKey["m", Modifiers-...

How to thread a list

I have data in format data = {{a1, a2}, {b1, b2}, {c1, c2}, {d1, d2}} Tableform: I want to thread it to : tdata = {{{a1, b1}, {a2, b2}}, {{a1, c1}, {a2, c2}}, {{a1, d1}, {a2, d2}}} Tableform: And I would like to do better then pseudofunction[n_] := Transpose[{data2[[1]], data2[[n]]}]; SetAttributes[pseudofunction, Listable]; Range[2, 4] // pseudofunction Here is my benchmark data, where data3 is normal sample of real data. data3 = Drop[ExcelWorkBook[[Column1 ;; Column4]], None, 1]; data2 = {a #, b #, c #, d #} & /@ Range[1, 10^5]; data = RandomReal[{0, 1}, {10^6, 4}]; Here is my benchmark code kptnw[list_] := Transpose[{Table[First@#, {Length@# - 1}], Rest@#}, {3, 1, 2}] &@list kptnw2[list_] := Transpose[{ConstantArray[First@#, Length@# - 1], Rest@#}, {3, 1, 2}] &@list OleksandrR[list_] := Flatten[Outer[List, List@First[list], Rest[list], 1], {{2}, {1, 4}}] paradox2[list_] := Partition[Riffle[list[[1]], #], 2] & /@ Drop[list, 1] RM[list_] := FoldList[Transpose[{First@li...

dynamic - How can I make a clickable ArrayPlot that returns input?

I would like to create a dynamic ArrayPlot so that the rectangles, when clicked, provide the input. Can I use ArrayPlot for this? Or is there something else I should have to use? Answer ArrayPlot is much more than just a simple array like Grid : it represents a ranged 2D dataset, and its visualization can be finetuned by options like DataReversed and DataRange . These features make it quite complicated to reproduce the same layout and order with Grid . Here I offer AnnotatedArrayPlot which comes in handy when your dataset is more than just a flat 2D array. The dynamic interface allows highlighting individual cells and possibly interacting with them. AnnotatedArrayPlot works the same way as ArrayPlot and accepts the same options plus Enabled , HighlightCoordinates , HighlightStyle and HighlightElementFunction . data = {{Missing["HasSomeMoreData"], GrayLevel[ 1], {RGBColor[0, 1, 1], RGBColor[0, 0, 1], GrayLevel[1]}, RGBColor[0, 1, 0]}, {GrayLevel[0], GrayLevel...