# Indexing error using sum

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Sordin on 19 May 2019
Edited: madhan ravi on 19 May 2019
I have written a simple code that performs a moving average smoothing algorithm (it averages n adjacent bins to a single bin similar to Matlab's smooth):
signal = ones(1,30); % Random sample
n=3; % An odd number (filter span)
for i = k : length(signal)-k
NewSignal(i,:) = sum(signal(i-n:i+n,:))/n;
end
However, the second to last line results in the following error:
%Index in position 1 is invalid. Array indices must be positive integers or logical values.
So, what is the cause of this error? And what would be a solution?
Any explanation would be greatly appreciated.
madhan ravi on 19 May 2019
Didn't test while commenting.

KALYAN ACHARJYA on 19 May 2019
Edited: KALYAN ACHARJYA on 19 May 2019
signal(i-n:i+n,:)
%.......^ here is the issue
When you run the code n=3 initial and k=2;
When you assigned i=k:... that menas first value is 2
signal(2-3:2+3,:)...
Which trsult >> signal(-1:5,:)
%.......................^......
Negative and zero index value is not allowed. index value must be positive integer only as stated in error message-
Array indices must be positive integers or logical values. Soln: If you want to use the same expression >>Modify the initial value such a way that k>n, ensure that k value is integer.
Learn array indexing here
KALYAN ACHARJYA on 19 May 2019
Commnent to @madhan ravi only today I have traced you in linkedIn. Great to see that you are too young. Keep it up and pls do continue to teach me in future too.
Gratitude to you!
Regards
Kalyan Acharjya

R2019a

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