How do I plot two variables on the same graph in matcont?

Hi there.

I'm currently using Matcont to simulate the oscillatory behaviour of protein regulation. This is a two variable system in which both mRNA and protein concentration are related two differential equations.

I am using matcont to solve these equations and plot the result. I am unable, however, to plot both the mRNA and protein concentration on a single axis.

Normally if I were using Matlab, I would simply type "hold on", however I cannot see an equivalent function anywhere in the matcont GUI.

I can easily plot either variable as a function of t, but I can't find anything that is able to plot both at the same time.

Answer 1

[Aashray]

Hi @Patric Boardman!

Yes, you have rightly noticed, in the ‘MatCont’ GUI the plotting is limited to showing one variable at a time versus time. There isn’t a built-in hold on equivalent or overlay option in the GUI itself, so it’s not possible to display mRNA and protein together on the same axis directly within ‘MatCont’.

A simple workaround is to export the computed solution to MATLAB and plot both variables together there. Here is how you can do the same in MATLAB:

1. In MatCont, after computing the solution, right-click the solution and export to the workspace. You will typically get a structure with fields like t (time) and x (state matrix).
2. Plot both series on the same axes with standard MATLAB commands as shown below

% Assuming MatCont exported a struct named "solution" 
t = solution.t;       % time vector 
x = solution.x;       % state variables (columns) 

% Column 1 = mRNA, Column 2 = protein 
figure; 
plot(t, x(:,1), 'b-', 'LineWidth', 1.5); hold on; 
plot(t, x(:,2), 'r--', 'LineWidth', 1.5); 
grid on; xlabel('Time'); ylabel('Concentration'); 
legend('mRNA','Protein', 'Location','best'); 
title('mRNA and Protein vs. time (exported from MatCont)'); 

This should reproduce the “hold on” overlay you are used to, while keeping MatCont for the simulation steps.