Question

I have the following matlab code for approximating a differential equation via the Euler-method:

% Eulermethod

a=0;
b=0.6;
Steps=6;
dt=(b-a)/Steps;
x=zeros(Steps+1,1);

x(1,1)=1;
y=zeros(Steps+1,1);

for i=1:Steps
    x(i+1,1)=x(i,1)+dt*(x(i,1)*x(i,1)+1);
end
plot(x)

I want to be able to plot the solution plot for several different values of Steps in one plot and have the x-axis go from 0 to 0.6 instead of from for example 1 to 100 000 etc. Can this be done?

Answer 1

If you use the hold on command this will allow you achieve multiple plots on the same figure. Similarly, if you separate your data into x and y vectors, you can plot them against eachother by passing 2 vectors to plot instead of just one. For example

figure
hold on
for i=1:m
    x = [];
    y = [];
    %% code to populate your vectors
    plot(x,y)
end

You should now see all your plots simultanesously on the same figure. If you want x to be composed of n equally spaced elements between 0 and 0.6, you could use the linspace command:

 x = linspace(0.0,0.6,n);

In order to distinguish your plots, you can pass an extra paramter to the function .For example

 plot(x,y,'r+')

will plot the data as a series of red + symbols.