How to plot a map with logarithmic colorbar and colormap with imagesc

Hello, I ask for your help since I've been trying to create maps with a logarithmic colormap and colorbar, but I haven't managed so far.

The problem is I have a loop through which I plot a number of maps using "imagescn", each map is referred to an hour of the day and represents the deposited kilograms of sediments into a lake due to a turbid input. Since the input changes a lot during the day, I want to be able to see in each plot values that range between 0 and 62 (maximum value of all times). As I'm doing now, nothing has changed and the colorbar and colormap are still linear, so that I can't see very well the smallest values . Also, I want the every plot in my loop has the same colorbar limits.

This is a part of my code: (i'm using MatlabR2021a)

for t = 10:10:200 %every t is referred to a time of the day
    figure(t)
    colormap('parula'); 
    my_clim=[0 62];
    c=[0 0.001 0.01 0.02 0.05 0.1 0.2 0.3 0.4 0.5 0.6 0.8 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32          33 34 35 36 37 38 39 40 45 50 55 60];
    data=array_data_rotated_t; %this array changes at each timestep and it is a 27x29 double array
    contourf(log(data(:,:)),log(c));
    colormap(parula); 
    caxis(log([c(1) c(length(c))]));
    colorbar('FontSize',11,'YTick',log(c),'YTickLabel',c);
    imagescn(array_data_rotated_t);
    h=colorbar;
end

Thank you for your help!

Francesca

[Walter Roberson]

c(1) is 0 and log(0) is -inf so you are asking to caxis from -inf which is going to be a problem

[Walter Roberson]

imagescn appears to be https://www.mathworks.com/matlabcentral/fileexchange/61293-imagescn

[Francesca Pisani]

Thank you, I've just tried to put the first number in c as 0.001 instead of 0, but nothing changed: the colorbar limits change for each figure and the colormap is not logarithmic. Imagescn works exactly as imagesc, except for the fact that NaN values are transparent.

Answer 1

[Sulaymon Eshkabilov]

for t = 10:10:200 %every t is referred to a time of the day
    figure(t)
    colormap('parula'); 
    my_clim=[0 62];
    c=[0 0.001 0.01 0.02 0.05 0.1 0.2 0.3 0.4 0.5 0.6 0.8 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32          33 34 35 36 37 38 39 40 45 50 55 60];
    data=array_data_rotated_t; %this array changes at each timestep and it is a 27x29 double array
    contourf(log(data(:,:)),log(c));
    colormap(parula); 
    caxis(log([c(1) c(length(c))]));
    colorbar('FontSize',11,'YTick',log(c),'YTickLabel',c);
    imagescn(array_data_rotated_t);
    h=colorbar;
    set(gca,'ColorScale','log')  % USE this command
end

[Francesca Pisani]

Thank you, it worked! One thing: how can I show 0 and 60 as min and max value in the colorbar labels?

[Walter Roberson]

    h=colorbar;
    h.Limit = [0 60];
    

Reminder: half of your c has a negative log so half of your contour levels would not get reflected in the colorbar ticks.

[Francesca Pisani]

Thank you, but unfortunately this shows an error: Unrecognized property 'Limit' for class 'matlab.graphics.illustration.ColorBar'.

I'm also trying to get one figure made of subplots, but I don't manage. For example, I've tried changing the loop saying :

figure(1)
for t=60:1:62
    fig=figure(1);
    sph{t} = subplot(3,1,t,'Parent',fig);
    contourf(sph{t},x,y,t.*z(:,:,t))               
    caxis(sph{t},[0,62]);

and keeping other lines as before. But I get the error:

    Error using subplot (line 319)
    Index exceeds number of subplots.
    
    Error in Deposited_mass_map (line 46)
    sph{t} = subplot(3,1,t,'Parent',fig);
    

Why does it happen? The number of subplots seems correct to me.

[Walter Roberson]

When you subplot(A, B, C) then C must not exceed A*B. subplot(3,1,t) then t must be 1 2 or 3 (or a vector of multiple values in that range)