matlab：量化数据并构建直方图

Question

I have a 3D data (X,Y,Z). Where X is between 0 to 360, Y is between 0 to 180 and Z is between -100 to + 100.

I'd like to quantize the data to NxM scale values on X and Y axes respectively and to have some mean value for Z.

This data shall be displayed on 2D plot where the Z values shall be represented by colors (if value is close to 100, then green, if the value is close to -100 then red). How this could be done?

I've seen that there is a histogram2 function, but it doesn't take into account the z values.

Answer 1

Not exactly sure if you intend to do a histogram specifically but here is one way to plot a set of z values on a xy-plane. The plot is created by viewing a 3D surface plot from its top view to give the impression that it is 2D. The view() function takes to arguments that's used to set the Angle and Elevation the plot is observed from. The colormap() function can be used to set your colours depending on the amplitude/magnitude of variable z . Below I used random data as an example.

The topic about quantizing data seems like it can be done by using a mean filter on blocks/windows of the z data. This will require more details and clarification. Any sample data will be greatly appreciated.

x = (0:360); 
y = (0:180);
z = (200*rand(length(y),length(x))) - 100;

[Time_Grid,Depth_Grid] = meshgrid(x,y);

surf(x,y,z);
title("Intensity Plot");
Angle = 0; Elevation = 90;
view(Angle,Elevation);

xlabel("x"); xlim([0,360]); 
ylabel("y"); ylim([0,180]);

red = [1 0 0]; green = [0 1 0]; blue = [0 0 1];

Colour_Palette = [red; blue; blue; blue; green];
colormap(Colour_Palette);
colorbar;