CODEWITHSUNDEEP
matlab
amirht
amirht

Reputation: 1

run a code on calculating the euler method for ODE

function yout = eulermethod(myeuler, t0, h, tf, y0)

 tic

    yout = y0 
    y = yout;

    for t = t0 : h : tf
        s = myeuler(t,y);
        y = y + h*s;
        y = y(2)
        yout = [yout; y]
        plot(t,yout)
    toc
    end

end

Igot this error Index in position 1 is invalid. Array indices must be positive integers or logical values.

Error in eulermethod (line 9) s = myeuler(t,y

Upvotes: 0

Views: 135

Answers (1)

Jamie Parkinson
Jamie Parkinson

Reputation: 86

The issue here is that MATLAB thinks myeuler is a matrix rather than a function. When you call eulermethod, I assume you are doing something like

yout = eulermethod(myeuler, t0, h, tf, y0);

What you actually want to be doing is

yout = eulermethod(@myeuler, t0, h, tf, y0);

The @ turns the first argument into a function handle (see the matlab documentation).

There are other issues with the rest of the code but I'm not exactly sure what equation you're trying to solve so I can't help too much. Certainly, your plot line doesn't make much sense as t is a scalar.

Assuming you're solving the differential equation dy/dt = 2y, for y(t=0) = y0, your functions should look a bit like

function dydt = myeuler(t,y)
dydt = 2*y;
end      

function yout = eulermethod(myeuler, t0, h, tf, y0)

    yout = y0;
    y = y0;

    for t = (t0+h):h:tf

        s = myeuler(t,y);
        y = y + h*s;
        yout = [yout; y];

        plot(t0:h:t, yout) 
        xlabel('t');
        ylabel('y');

        pause(0.1);

    end

end

And would then be called by some code like

t0 = 0;
h = 0.01;
tf = 1;
y0 = 1.0;

yout = eulermethod(@myeuler, t0, h, tf, y0);

Upvotes: 1

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