How to find the value of a function for different input?

hello !

lets say i have a function f(x)=x^2+3*x;

i want to find the function vaslues from x=1 to x=20.

how to write the code for the above ?

syms x
f=x^2+3*x;
for i=1:20
    f(i);
end

above code is showing error. please provide your input !

Answer 1

[KSSV]

Multiple methods:

Method # 1 Anonymous functions

f = @(x) x.^2+3*x ; 
x = linspace(1,20,100) ; 
y = f(x) ; 
plot(x,y)

Method # 2 Using arrays

x = linspace(1,20,100) ; 
y = x.^2+3*x ; 
plot(x,y)

Method # 3 using syms

syms x 
f(x) = x^2+3*x ;
double(f(3))