I am having problems changing this code so that it includes FUNCTION in Matlab. I made the code so takes one specific equation but need it edited so it takes any equation. EDIT CODE SO THAT USES FUNCTION IN MATLAB

Let the function is f(x) = 8 - x^2
f = @(x) 8-x.^2;
% Let us take a Riemann sum over [-2,2] at dx =0.5
dx=0.5;
x=-2:dx:2;
R_sum =0;
for i=1:length(x)
R_sum = R_sum + f(x(i)+dx/2)*dx; % Mid point Riemann sum
end
display(R_sum)
% Let us apply Trapezoidal rule over [-2,2] at dx =0.5
T_sum = 0;
for i=1:length(x)-1
T_sum = T_sum + (f(x(i+1))+f(x(i)))*dx/2;
end
display(T_sum)

figure(1)
grid on
hold on
bar(x,f(x),1,'y'); %ploting rectangles for Riemann sum
hold on
xp=-2:0.01:2; %ploting the function
plot(xp,f(xp),'b')

figure(2)
grid on
hold on
% ploting the trapezoids
for i=1:length(x)
plot([x(i),x(i)],[0,f(x(i))],'r'); % Ploting the vertical lines
hold on
end
for i=1:length(x)-1
% Ploting the non-parallal lines
plot([x(i+1),x(i)],[f(x(i+1)),f(x(i))],'r')
hold on
end
xlim([min(x)-0.5,max(x)+0.5])
hold on
plot(xp,f(xp),'b') %ploting the function

[Rik]

What is your question? Do you want to convert your script into a function?