Both Pcolor color plot and quiver plot in log scale

Hai,

I need to plot pcolor plot with y-axis in log scale and over plot with quiver plot in log scale.

Please help me how to do this.

Here is my code:

pcolor(1:365,pr(:,1),Ez1.*10^6);shading interp; colormap('jet(25)');colorbar;set(gca,'YScale','log');
hold on ; quiverInLogScale(1:15:365,MP,Zu1(:,1:15:365),Zv1(:,1:15:365))%,2,'-k')
set(gca,'Ydir','reverse');
caxis([0 8]);
ylim([1  100]);%xlim([0 396]);
title('(a) Daily mean (2005:2021) H2O (ppmv)')
set(gca, 'XTick',     [1 31 59 90  120 151 181 212 243 273 304 335 365]);
set(gca,'XTickLabel', {'1' '31' '59' '90' '120' '151' '181' '212' '243' '273' '304' '335' '365'})
ylabel('P (hPa)')
set(gca, 'YTick',     [1     10   21.54	 31.62	 	     56.23		      100]);
set(gca,'YTickLabel', {'1',	'10','21.54','31.62','56.23','100'})
colormap(ax1,jet(20)), colorbar

Answer 1

[Abhinaya Kennedy]

To plot a pcolor plot with a logarithmic y-axis and overlay it with a quiver plot also in a logarithmic scale, you need to ensure that both plots are consistent with the log scale.

% Data setup (assuming pr, Ez1, MP, Zu1, and Zv1 are already defined)
% pr should be a column vector representing the y-axis values
% Ez1 should be a matrix for the pcolor plot
% MP should be a column vector representing the y-axis values for the quiver plot
% Zu1 and Zv1 should be matrices for the quiver plot

% Create the pcolor plot
figure;
pcolor(1:365, pr(:, 1), Ez1 .* 10^6);
shading interp;
colormap('jet(25)');
colorbar;
set(gca, 'YScale', 'log');
hold on;

% Adjust MP to log scale for the quiver plot
logMP = log10(MP);
logMP = logMP - min(logMP); % Normalize to avoid negative values
logMP = logMP / max(logMP); % Scale to [0, 1]
logMP = 10 .^ (logMP * (log10(max(pr)) - log10(min(pr))) + log10(min(pr))); % Scale back to original range

% Create the quiver plot
quiver(1:15:365, logMP, Zu1(:, 1:15:365), Zv1(:, 1:15:365), 2, '-k');

% Set properties
set(gca, 'Ydir', 'reverse');
caxis([0 8]);
ylim([1 100]);
title('(a) Daily mean (2005:2021) H2O (ppmv)');
set(gca, 'XTick', [1 31 59 90 120 151 181 212 243 273 304 335 365]);
set(gca, 'XTickLabel', {'1', '31', '59', '90', '120', '151', '181', '212', '243', '273', '304', '335', '365'});
ylabel('P (hPa)');
set(gca, 'YTick', [1 10 21.54 31.62 56.23 100]);
set(gca, 'YTickLabel', {'1', '10', '21.54', '31.62', '56.23', '100'});

% Adjust colormap and colorbar
colormap('jet(20)');
colorbar;

1. Logarithmic Scaling of MP: The MP array is transformed to a logarithmic scale to match the y-axis of the plot.
2. Normalization and Scaling: The logMP variable is normalized and scaled back to the original range to ensure proper placement on the logarithmic y-axis.

This should give you a pcolor plot (https://www.mathworks.com/help/matlab/ref/pcolor.html) with a logarithmic y-axis and an overlaid quiver plot (https://www.mathworks.com/help/matlab/ref/quiver.html) that is consistent with the logarithmic scale.