Hold on command in ode45

I want to plot the graph of first order ODE y'=ax for different numerical values of 'a' in the same graph using ode45. I tried using 'hold on' command but it is not working. could anyone tell me how to do that?

Answer 1

[Davide Masiello]

You could do this.

clear,clc

a       = linspace(0.1,0.2,10);                 % 'a' takes 10 values between 0.1 and 0.2
tspan   = [0,10];                               % Time span of integration
y0      = ones(size(a));                        % Initial conditions 
[t,y]   = ode45(@(t,y)myode(t,y,a'),tspan,y0);  % Passes function to ode solver

plot(t,y)                                       % Plots results
legend(string(a),'Location','northwest')        % Displayes legend

function out = myode(t,~,a)
out = a.*t;
end

Which result is

EXPLANATION:

There is no need to use 'hold on', because you can first integrate the equation for every value of 'a' and then plot them all together.

A way of doing this could be to put the 'ode45' call in a 'for loop' and change the value of 'a' at each iteration.

However, the solution I provided solves all the equations together saving a bit of time and lines of code.