How to plot points on map axes with varying colors using scatterm?

Question

Samuel 2023-6-15

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https://ww2.mathworks.cn/matlabcentral/answers/1983884-how-to-plot-points-on-map-axes-with-varying-colors-using-scatterm

回答： Malay Agarwal 2023-6-16

Lin14_cores.csv

I have three vectors: lat, lon, depth. They are of equal length. When I run the code below, I get an error saying: Error using scatter

Color must be one RGB triplet, an m-by-3 matrix of RGB triplets with one color per scatter point, or an m-by-1 vector with one value per scatter point.". I don't understand, because my depth vector, which is being used for color, is the same size as my latitude vector.

%Load in data
data = readmatrix("Lin14_cores.csv","NumHeaderLines",1);
lon = data(:,1);
lat = data(:,2);
depth = data(:,4);
%Plot datapoints on map axes with colors showing depth
load coastlines
ax = axesm("MapProjection","mollweid","MapLatLimit",[-60 60], "MapLonLimit",[-180 180], 'Frame', 'on');
plotm(coastlat,coastlon)
scatterm(ax, lat,lon, ones(length(lat))*50, depth);
colormap("autumn")

Can anyone help me fix this.

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Answer 1

Malay Agarwal 2023-6-16

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https://ww2.mathworks.cn/matlabcentral/answers/1983884-how-to-plot-points-on-map-axes-with-varying-colors-using-scatterm#answer_1257099

在 MATLAB Online 中打开

plot.jpg

Hi Samuel,

I think the issue is with the way the depth array is being passed. When you're passing colors as a m-by-1 vector, each value can be one of the supported values specified here: Project scatter plot on axesm-based map - MATLAB scatterm. You cannot use the m-by-1 format with RGB values. If you want to do that, you should be passing in a m-by-3 matrix of RGB triplets where each value in the triplet is between 0 and 1. For example, the code below will create the attached plot:

data = readmatrix("Lin14_cores.csv","NumHeaderLines",1);
[m, ~] = size(data);
lon = data(:,1);
lat = data(:,2);
% Red color
color = [1 0 0];
% Repeat the vector m times to get an m-by-3 matrix
colors = repmat(color, m, 1);
load coastlines
ax = axesm("MapProjection","mollweid","MapLatLimit",[-60 60], "MapLonLimit",[-180 180], 'Frame', 'on');
plotm(coastlat,coastlon)
% Notice how the last argument is colors instead of depth
scatterm(ax, lat,lon, ones(length(lat))*50, colors);
colormap("autumn")