conditional statement with for loop - matlab

Question

Not sure what I am doing wrong here;
I am trying to make a for loop with conditional statements for the following functions. I want to make it though so h is not a vector. I am doing this for 1 through 5 with increment 0.1.
Y = f(h) = h^2 if h <= 2 or h >= 3
Y = f(h) = 45 otherwise
my code is
for h = 0:0.1:5
if h <= 2;
Y = h^2;
elseif h >= 3;
Y = h^2;
else;
h = 45;
end
end

Answer 1

This could be done easier, but with a for loop i think you could use:
h=0:0.1:5;
y=zeros(1,length(h));
for i=1:length(h)
if or(h(i) <= 2, h(i) >= 3)
y(i) = h(i)^2;
else
y(i) = 45;
end
end

Answer 2

Why do you want to avoid making h an array? MATLAB specializes in operations on arrays. In fact, vectorized operations in MATLAB are generally faster than for loops, which I found counter-intuitive having started coding in C++.
An example of a vectorized verison of your code could be:
h = 0:0.1:5;
inds = find(h > 2 & h < 3); % grab indices where Y = 45
Y = h.^2; % set all of Y = h^2
Y(inds) = 45; % set only those entries for h between 2 and 3 to 45
The period in the .^2 operator broadcasts that operator to every element in the h array. This means that you end up squaring each number in h individually. In general, vectorized operation like this are more efficient in MATLAB, so it is probably best to get in the habit of vectorizing your code.
Finally, you could reduce the above code a bit by not storing your indices:
h = 0:0.1:5;
Y = h.^2; % set all of Y = h^2
Y(find(h > 2 & h < 3)) = 45; % set only those entries for h between 2 and 3 to 45
This blog series seems to be a good primer on vectorizing your MATLAB code.