How can I plot a matrix using pcolor and colorscale as log?

I have a timeseries matrix data of a lidar. I want to plot the time series keeping colorbar as logscale.

I have written the following code but it shows an error

load time_June.mat

load elevation_June_5km.mat

load backscatter_June_5km.mat

load raw_backscatter_June_5km.mat

figure(1);

pcolor(time_June, elevation_June_5km, backscatter_June_5km); shading interp

c = colorbar;

caxis([10^-7 10^-4]);

set(gca, 'ColorScale', 'log');

c.Label.String = 'Attenuated backscatter coefficient (m^{-1} sr^{-1})';

c.Ruler.Scale = 'log';

c.Ruler.MinorTick = 'on';

colormap jet;

set(gca, 'YDir', 'normal');

xlabel('Time (LT)');

ylabel('Altitude (km)');

axis tight;

set(gca, 'FontName', 'Times', 'FontSize', 14);

startDate = datetime(2023, 6, 16);

endDate = datetime(2023, 6, 25);

xlim([startDate, endDate]);

Error:

Warning: Error creating or updating Surface

Error in value of property CData

DataSpace or ColorSpace transform method failed.

[Sahas]

Hi @AMIT SINGH CHANDEL,

I've taken a look at the code and ran a few simlations with dummy data. But to generate the given errors, it would requires the specific files to load the workspace variables. Could you please share those files so that I could further investigate for the cause of this behaviour?

[AMIT SINGH CHANDEL]

Hi Sahas

I have attached the files for you to look over.

Answer 1

[Star Strider]

According to the ColorScale documentation, that property should set the colorbar scale as well.

I would not use pcolor. The best option would likely be to use surf and view, spedifically view(2).

[AMIT SINGH CHANDEL]

I used surf, even then the error is same. Warning: Error creating or updating Surface

Error in value of property CData

DataSpace or ColorSpace transform method failed.

[Star Strider]

I cannot figure out what you are doing. I also do not have your data, so I cannot experiment with it.

Using an example from Specify True Colors for Surface Plot and adding a ColorScale call, I get this result —

[X,Y,Z] = peaks(25);
CO(:,:,1) = zeros(25); % red
CO(:,:,2) = ones(25).*linspace(0.5,0.6,25); % green
CO(:,:,3) = ones(25).*linspace(0,1,25); % blue

figure
surf(X,Y,Z,CO)
Ax = gca;
Ax.ColorScale = 'log';
colorbar

.

[Star Strider]

It works in R2024a without error,so perhaps an upgrade would be appropriate.

Note that your desired dates (at least for this data set) are not included in the ‘time_June’ datetime array.

files = dir('*.mat');
NrFiles = numel(files)

NrFiles = 3

for k = 1:numel(files)
    filename = files(k).name
    vars = whos('-file', filename);
    varname = vars.name;
    load(filename)
    Sz = vars.size
end

filename = 'backscatter_June_5km.mat'

Sz = 1x2

500 5760

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filename = 'elevation_June_5km.mat'

Sz = 1x2

500 1

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filename = 'time_June.mat'

Sz =

     []

figure(1)
% surf(backscatter_June_5km, 'EdgeColor','interp')
surf(time_June, elevation_June_5km, backscatter_June_5km, 'EdgeColor','interp')
c = colorbar;
caxis([10^-7 10^-4]);
set(gca, 'ColorScale', 'log');
c.Label.String = 'Attenuated backscatter coefficient (m^{-1} sr^{-1})';
c.Ruler.Scale = 'log';
c.Ruler.MinorTick = 'on';
 
colormap jet;
set(gca, 'YDir', 'normal');
xlabel('Time (LT)');
ylabel('Altitude (km)');
axis tight;
set(gca, 'FontName', 'Times', 'FontSize', 14);

startDate = datetime(2023, 6, 16);
endDate = datetime(2023, 6, 25);
CheckDates = nnz(ismember(time_June, [startDate, endDate]))

CheckDates = 0

time_June_Range = [min(time_June); max(time_June)]

time_June_Range = 2x1 datetime array
   01-Jun-2023 00:00:00
   02-Jun-2023 23:59:30

% xlim([startDate, endDate]);

.