How do I select and/or delete values of a certain index in an array?

I have a data set (OrbSolPwr) in a 2880 x 1 double array. I only want the first (n) terms. How do I either select the first (n) terms into a new array or delete the (n+1):numel(OrbSolPwr) terms? (Using the R2016a student/academic version)

n = 1261;
m = numel(OrbSolPwr);    % m = 2880
for i = 1:m;
    if i > n:
       OrbSolPwr(i,1) = [];
    end
end

First try gives the error that a null assignment can have only one con-colon index for line 5 above. I realize that the index would also get messed up since the length will change as the data set shrinks, but I don't know how to write that.

n = 1261;
m = numel(OrbSolPwr);    % m = 2880
for i = n+1:m;
    OrbSolPwr(i,1) = [];
end

I also tried this, which gives the same error as before.

Answer 1

[Nick]

This is how you would extract the data to a new array

 %Generate random numbers for Example
 OrbSolPwr = randi(10,2880,1);

 %Select cutoff
 n = 15;
 newOrbSolPwr = zeros(n,1);

 %Extract values from old data to new data
 for i = 1:n
    newOrbSolPwr(i) = OrbSolPwr(i);
 end

if you wanted to delete the elements. The index will keep shrinking but its ok because we are iterating by a negative 1 so it won't exceed the matrix dimensions

   m = numel(OrbSolPwr)
   for i = m:-1:n+1
      OrbSolPwr(i) = [];
   end

Answer 2

[Image Analyst]

Nick's solution is like what you'd do in C or Java, not MATLAB. In MATLAB, you simply do it in one line of code by extracting the rows you want:

OrbSolPwr = OrbSolPwr(1:n);

Any elements after n are discarded. No for loop is needed at all because MATLAB is a vectorized language.