How to create a function in the editor, then evaluate the function and plot the function.

Hello all,

I am typing this function into the editor, and my goal is to evaluate the function at some points, and plot the function. Here is what I am typing in the editor.

function anon1
f=@(x) x^3 + 2x^2 - x
a=-10;
b=10;
TOL=.001

So, to evaluate the function at x=3 what do I type in the command window? And how do I apply the form given to plot. The form is fplot(fun,limits).

I was under the impression that I could just type anon1(3) to evaluate, but an error is showing.

Thanks

Answer 1

[Youssef Khmou]

Hi, Truxton,

In your code : you did two different things, making a function in M-file but inside that function , you used also "function_handle", you have two ways :

1) You create a function with its own Input/Output :

function [y]=Truxton(x)   % function output=function_name(input)

   y=x.^3 + 2*x.^2 - x;
   a=-10;
   b=10;
   TOL=.001

Now in the command prompt , you tape per example :

>>x=5;z=Truxton(x)
>>time=[0:pi/100:10*pi];
>>Z=Truxton(time);
>>plot(time,Truxton)
>>fplot('Truxton',[0 100])

2)Or you can use the function handle directly in the command prompt :

 >>f=@(x) x.^3 + 2*x.^2 - x
 >>z=f(5);
 >>z2=f([0:0.01:10];

I hope that helps

[Truxton]

Thanks, it did!

Answer 2

[Azzi Abdelmalek]

f(3)

to plot

f=@(x)x^3 + 2*x^2 - x
a=-10;
b=10;
fplot(f,[a,b])

[Truxton]

Thanks, I got it!