Finding Roots of Functions with Matlab

[yohak]

Homework Statement

I need to find the roots of some functions using the bisection method, secant method, etc in Matlab. I have the m-files written, but I'm having trouble putting the function F(x)=e^{-0.5x}(4-x)-2 into Matlab. I had no problem with F(x)=0.95x^{3}-5.9x^{2}-6 but I don't know what to do about the exponential.

I'm also having trouble getting feval to work. I got around it by using polyval, but although it works for F(x)=0.95x^{3}-5.9x^{2}-6 I don't know if it will work for every function.

Homework Equations

none

The Attempt at a Solution

I'm kind of new to Matlab, but I understand that polynomials are entered as a single row vector (example: F(x)=0.95x^{3}-5.9x^{2}-6 is entered as [0.95 -5.9 0 -6]) but I don't know how to put this function in since it is an exponential.

Is polyval a valid solution to the feval issue? The error says "Argument must contain a string or function_handle" but I don't know what that means.

 

[MATLABdude]

I don't know if this is what you're looking for, but you can use inline functions to simplify function evaluation:
http://www.mathworks.com/help/techdoc/ref/inline.html

This comes in quite handy when doing iterative functions as it sounds like you're doing.

 

[jhae2.718]

You could create an anonymous function, e.g.:

f = @([I]arg_list[/I]) [I]expression[/I];

where arg_list are the function arguments and expression is the function, and f is the name of the anon function.