Polynomial as input in a function.

I am trying to make a function which takes a polynomial, a maxvalue of x and a minvalue of x. I want to plot the function between max and min with 1000 points.

this is what i have come up with so far:

function [] = Oppgave2(funksjon, intervallMin, intervallMax)
figure
%a
x = [intervallMin:((abs(intervallMin)+abs(intervallMax))/1000):intervallMax]; %Here i create the 1000 points between min and max.
plot(x, funksjon); %Display the function in a figure
end

I want to be able to input funksjon as x.^2-3.*x+2 for example, but i cant make it work. The solution is probably really simple but i am very new to programming in matlab.

Thanks in advance!

Answer 1

[KSSV]

LEt a, b be your max and min values

x = linspace(a,b,1000) ; 
p = 2*x.^2+3*x+5 ;  % polynomial
plot(x,p)

[Kristoffer Søhagen]

Thats a better way to to get the x values! Thanks! But my main problem is that matlab doesnt like when in call the function like this:

Oppgave2(x.^2-3.*x+4, -5, 5)

I get this error message: Unrecognized function or variable 'x'.

[KSSV]

You cannot input like this. USe like below:

x = linspace(a,b,1000) ; 
f = @(x) 2*x.^2+3*x+5 ; 
p = f(x) ;  % polynomial
plot(x,p)

[Kristoffer Søhagen]

Yeah, that works. But i want to make a function i can call from other scripts to plot a polynomial between a and b. If it is possible.

Example:

function(polynomial, a, b)

function(x.^2+3.*x-4, -5, 5)

[KSSV]

a =1 ;b = 10 ;
f = @(x) 2*x.^2+3*x+5 ; 
p = mypoly(f,a,b) ; 

function p = mypoly(f,a,b)
x = linspace(a,b,1000) ; 
p = f(x) ;  % polynomial
plot(x,p)
end

[Kristoffer Søhagen]

Great! Thank you!