Plot a composite function with two y axis, with one of them scaling according to a function

Hi all,

I want to plot a composite function on a Matlab plot with two y axes. I have 3 variables: position, intensity and temperature. Position is the x one, on the horizontal axis. Intensity and temperature have to go on the y axes. However, intensity and temperature are related to each other by a logarithmic function, for which I know the equation. If I use yyaxis left and yyaxis right, I obviously get that x and y scale linear, both on the left and on the right, so I get two plots that don't superimpose. Is there a way to scale the right axis according to the known relationship between intensity and temperature, so that in the end I get only one plot?

Thanks!

for i=1:5
yyaxis left
h1=plot(pos_S1(:,i),intensity_S1(:,i),'o','color',colors(i,:));
set(h1, 'markerfacecolor', get(h1, 'color'),'markersize',2);
hold on
ylabel('Normalized intensity [-]');
yyaxis right
h2=plot(pos_S1(:,i),temperature_S1(:,i),'o','color',colors(i,:));
set(h2, 'markerfacecolor', get(h1, 'color'),'markersize',2);
hold on
set(gca, 'Ydir', 'reverse')
ylabel('Temperature [\circC]');
xlabel('Position [\mum]','FontSize',16)
end

Answer 1

[Chetan]

Hi @Alessia,

I understand you're aiming to plot intensity and temperature against position on a MATLAB plot featuring two y-axes.

To accomplish this, plot the intensity on the left y-axis and manually adjust the right y-axis (temperature) to mirror the logarithmic relationship with intensity.

This step involves customizing tick marks and labels on the right y-axis post-plotting.

Here is the sample code for the same:

% Example of plotting and adjusting y-axis scales
yyaxis left
plot(pos_S1(:,1), intensity_S1(:,1), 'o'); % Plotting intensity
ylabel('Intensity');
yyaxis right
plot(pos_S1(:,1), temperature_S1(:,1), 'o'); % Plotting temperature
ylabel('Temperature');
% Adjusting the right y-axis to align with the logarithmic relationship
% Calculating corresponding temperatures for a range of intensities
intensity_range = linspace(min(intensity_S1(:)), max(intensity_S1(:)), 10);
temperature_ticks = log(intensity_range); % Using a simple log relationship for illustration
% Applying calculated temperatures as tick labels (adjust according to your relationship)
set(gca, 'YTick', temperature_ticks, 'YTickLabel', arrayfun(@num2str, temperature_ticks, ...
    'UniformOutput', false));

Please ensure to modify the `log(intensity_range)` part to accurately reflect your specific logarithmic relationship between intensity and temperature.

Refer to the following MathWorks Documentation for more details:

• https://www.mathworks.com/help/matlab/ref/yyaxis.html
• https://www.mathworks.com/help/matlab/ref/axes.html

Thanks

Chetan