MATLAB: Trapezium Rule example won’t work

functiontrapezium rule

I do not understand why this code is not working? I am trying to estimate the integral of e^-x2 between x=0 and x=2 using the trapezium rule

Best Answer

You're combining a function declaration and a function call.

Call your function something other than trapz because that's already a function in MATLAB. Let's call it IssieTrapz. It takes four input arguments, which I suspect your function accepts in the following order:

function I = IssieTrapz(f, a, b, n)

This is line 1 of your function. It replaces your original line 1. That's the declaration of the IssieTrapz function.

Now when you call IssieTrapz, that's when you specify the function and give values for a, b, and n.

result = IssieTrapz(@(x) exp(-x^2), 0, 2, 10);

Related Solutions

MATLAB: Fsolve not enough input arguments

You need to supply System() as a function handle to fsolve(). The way you have written it, Matlab thinks you want to simply call the function System(), and supply the result to fsolve().

As far as I know, the script itself should not execute because you can't define functions within scripts.

clc, clear
x0 = [1, 1, 1, 1,1];
Coefficients = fsolve(@(x)System(x), x0)

In a separate file (also, it looks like your function "System" will also not return an output, so need to change the output name):

function F = System(x)
F = nan(1,6);
F(1) = x(1)*[exp(x(4)/x(2)) - exp(-x(4)/x(3))] - 0.9;
F(2) = x(1)*[exp(-(x(4)-0.6*1.2e-6)/x(2)) - exp(-(x(4)-0.6*1.2e-6)/x(3))] - 0.3;
F(3) = x(1)*[exp(-50e-6/x(2)) - exp(50e-6/x(3))] - 0.5;
F(4) = x(1)*[exp(-x(5)/x(2)) - exp(-x(5)/x(3))] - 1;
F(5) = -x(1)/x(2)*exp(-x(5)/x(2)) + x(1)/x(3)*exp(-x(5)/x(3));
F(6) = 30e3*x(1)*(exp(-x(4)/x(2)-exp(-x(4)/x(3)))) - 30e3*x(1)*(exp(-(x(4)-0.6*1.2e-6)/x(2))-exp(-(x(4)-0.6*1.2e-6)/x(3)));
end

I would also ask about the math problem, which looks over-specified...5 unknowns in 6 equations

MATLAB: Defining functions with exponentials

In the very first line of your code, you misplaced the '*' (you placed it right after the 'exp' expression. I tried the following code by myself and it worked flawlessly. I hope my answer was helpful.

% This one should work:

F=[-data + (x(1)*x(2)*((1- exp((-x(1)-((x(3)*x(4))/(x(4)+(x(3)-x(4))*exp(-x(5)*v))))*t))/... (x(1) + ((x(3)*x(4)) / (x(4)+((x(3)-x(4))*exp((-x(5)*v)))) * exp(-x(1) - ((x(3)*x(4))) /( x(4)+(x(3)-x(4))*exp((-x(5)*v))))*t))))]; res=sum(F.^2)

Best Answer

Related Solutions

MATLAB: Fsolve not enough input arguments

MATLAB: Defining functions with exponentials

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