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

plotting - How to draw lines between specified dots on ListPlot?

I would like to create a plot where I have unconnected dots and some connected. So far, I have figured out how to draw the dots. My code is the following: ListPlot[{{1, 1}, {2, 2}, {3, 3}, {4, 4}, {1, 4}, {2, 5}, {3, 6}, {4, 7}, {1, 7}, {2, 8}, {3, 9}, {4, 10}, {1, 10}, {2, 11}, {3, 12}, {4,13}, {2.5, 7}}, Ticks -> {{1, 2, 3, 4}, None}, AxesStyle -> Thin, TicksStyle -> Directive[Black, Bold, 12], Mesh -> Full] I have thought using ListLinePlot command, but I don't know how to specify to the command to draw only selected lines between the dots. Do have any suggestions/hints on how to do that? Thank you. Answer One possibility would be to use Epilog with Line : ListPlot[ {{1, 1}, {2, 2}, {3, 3}, {4, 4}, {1, 4}, {2, 5}, {3, 6}, {4, 7}, {1, 7}, {2, 8}, {3, 9}, {4, 10}, {1, 10}, {2, 11}, {3, 12}, {4, 13}, {2.5, 7}}, Ticks -> {{1, 2, 3, 4}, None}, AxesStyle -> Thin, TicksStyle -> Directive[Black, Bold, 12], Mesh -> Full, Epilog -> { Line[ ...

equation solving - Invert and fit implicitly defined curve

I need to fit an implicitly defined curve. I thought I could get some data out of Solve , and then using FindFit . Therefore, I would like to find the relation the parametric curve defined by $F(x,y)=0$: Solve[-(1/2) + 1/2 (0.41202 BesselK[0, 0.1 Sqrt[x^2 + y^2]] + (0.101483 x BesselK[1, 0.1 Sqrt[x^2 + y^2]])/Sqrt[x^2 + y^2]) == 0, y] But I can't get an output: Solve was unable to solve the system with inexact coefficients or the system obtained by direct rationalization of inexact numbers present in the system. Since many of the methods used by Solve require exact input, providing Solve with an exact version of the system may help. >> Edit: In particular, I would like to fit the data coming from the curve with the expression of another curve, and not with a function $f(x)$. In particular, since this clearly looks like a cardioid , I would like it to fit to something like it. What other strategies could I try?

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...