How can I find the value of a function at some point in Matlab?

Question

For example, if I define the following in Matlab,

f(x) = x^2 + 3x - 2

How do I find what value the function evaluates to when x = 3?

Answer 1

Create a file called fm that contains:

function y = f(x)
y = x^2 + 3x - 2

then in the command window, type f(3) and you should get back ans=16

See documentation on creating functions in MATLAB: http://www.mathworks.com/help/techdoc/ref/function.html

You can also use polyval(p,x) where p = [1 3 -2] in your example (the coeffients of your polynomial in descending order) and you will get the value of the polynomial at that point x (in your case, you would pass in 3).