MATLAB: Help with basics and finite difference method

beginner

I have to write a program using the finite-difference formula to calculate the approximate value for the derivative of a function. The test will be tan(x) for x=1, determining the error by comparing with sec^2(x). I have no idea where to begin.

Best Answer

How about a for loop and taking the delta Y over the delta X where the separation is decreasing until it gets really really small, then compare to sec^2(x) and see how the difference gets smaller and smaller as the separation gets smaller and smaller. That's the finite difference method.

http://www.mathworks.com/matlabcentral/answers/8626-how-do-i-get-help-on-homework-questions-on-matlab-answers

Related Solutions

MATLAB: Forward, backward and central differences

Fun = @(x) exp(-x).*sin(3*x); 
dFun = @(x) -exp(-x).*sin(3*x)+ 3*exp(-x).*cos(3*x);
x=linspace(0,4,101);
F=Fun(x);
h=x(2)-x(1);
xCentral=x(2:end-1);
dFCenteral=(F(3:end)-F(1:end-2))/(2*h);
xForward=x(1:end-1);
dFForward=(F(2:end)-F(1:end-1))/h;
xBackward=x(2:end);
dFBackward=(F(2:end)-F(1:end-1))/h;
plot(x,dFun(x));
hold on
plot(xCentral,dFCenteral,'r')
plot(xForward,dFForward,'k');
plot(xBackward,dFBackward,'g');
legend('Analytic','Central','Forward','Backward')

MATLAB: How can i change x to (x+h)

I am not certain what problem you are having. You have to define all the values you pass to your function as arguments before calling your function.

Example —

f = @(x) x.^2- 4;
h = 1E-8;
dfdx = @(f,x,h) (f(x+h) - f(x))./h;
x = 4;
fval = f(x)
derv = dfdx(f,x,h)

Best Answer

Related Solutions

MATLAB: Forward, backward and central differences

MATLAB: How can i change x to (x+h)

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