Plotting a heatmap with collected data

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jason.dim 2022-3-10

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https://ww2.mathworks.cn/matlabcentral/answers/1668094-plotting-a-heatmap-with-collected-data

评论： Simon Chan 2022-3-16

I have an image of a map with data allocated to different points on the map. Am I able to get co-ordinates of that image to place the data it's allocated spots and produce a heatmap over the image? Perhaps there is a better way of doing this?

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KSSV 2022-3-10

Okay can be done...Have a look on geoscatter.

jason.dim 2022-3-10

Thanks for the help. I will look into it.

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采纳的回答

Simon Chan 2022-3-10

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1668094-plotting-a-heatmap-with-collected-data#answer_914309

在 MATLAB Online 中打开

map.png

Use function pcolor is another option.

clear;clc;

im = imread('map.png');

[Ny,Nx,Nc] = size(im);

f = figure(1);

ax = gca;

minSignal = 20;

maxSignal = 800;

X = repmat(linspace(minSignal,maxSignal,Nx),Ny,1); % Dummy data only

h = imagesc(ax,1:Nx, 1:Ny,im);

hold(ax,'on');

s=pcolor(ax,X);

s.FaceColor = 'interp';

s.FaceAlpha = 0.5;

s.EdgeColor = 'none';

axis(ax,'image');

cmap = colormap(ax,hsv);

cb = colorbar(ax);

title(cb,'Signal Level');

axis(ax,'off');

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Simon Chan 2022-3-11

在 MATLAB Online 中打开

map.png

You may refer to this link: Array Indexing to understand more about the indexing in MATLAB.

Suppose your data is across the map in lateral direction (from left to right).

I would resize the image in this direction so that I am able to put the data without any interpolation.

In the following example, the number of row and column of the original image (Variable im) are 342 and 430 respectively. I don't care the number of rows since your data has only 1 row, so I resize the number of columns from 430 to 420 so that all data can be fitted just by repeating the data.

The next step is to repeat the signal to match the number of the columns in the image. For each signal, it occupy 20 columns in the image. After that, repeat the expanded signal in row direction, which is 342 in this case.

clear;clc;

im = imread('map.png');

[Ny,Nx,Nc] = size(im); % Determine the size of the image

Sig = [-104 -97 -105 -99 -95 -83 -95 -109 -104 -105 -82 -85 -89 -104 -97 -103 -83 -84 -84 -84];

Nz = length(Sig); % Number of data in the signal

extra_Nx = mod(Nx,Nz);

im_resize = imresize(im, [Ny,Nx-extra_Nx]); % Resize the image based on number of the signal

[~,Nx_new,~] = size(im_resize);

rep_Sig = repelem(Sig,1,Nx_new/Nz); % Repeat signal to fit column number of the image

rep_Sig = repmat(rep_Sig,Ny,1); % Repeat signal to fit row number of the image

f = figure(1);

ax = gca;