Clear Filters
Clear Filters

summation without using any loop algorithm

3 views (last 30 days)
Hello,
I am trying to implement the summation for a square wave without the use of loops. I have the following code:
sona = sin((2*k - 1)'*t)./(2*k - 1);
but keep getting the error: "Error using * Inner matrix dimensions must agree"
Can you please explain what the problem is and how I can fix this error?
Thanks, monkey_matlab

Accepted Answer

Walter Roberson
Walter Roberson on 24 May 2015
Suppose that your k is a row vector of 1:n
k = 1:n;
and suppose that your t is a row vector of length L
L = 50;
t = linspace(0,20,L);
then
(2*k-1)' * t
would be well defined and would be of size n x L. You can sin() that and the result will stay n x L. Now you are trying to divide it by the row vector (2*k-1). An n x L matrix cannot be divided by a 1 x n row vector. So you need to extend the 1 x n row vector into an n x L matrix in order to do the division:
repmat((2*k-1)', 1, L)
now you can do element-by-element division, and that is going to give you an n x L result. If you now sum along the first dimension, you would get a 1 x L result:
n = 16; %number of harmonics
startat = 0; %start and stop times
endat = 20;
L = 50; %how many time points
k = 1:n;
k21 = 2*k - 1;
t = linspace(0,20,L);
sona = sum(sin(k21' * t) ./ repmat(k21', 1, L), 1);
plot(t, sona)

More Answers (0)

Categories

Find more on MATLAB in Help Center and File Exchange

Tags

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!