MATLAB: Moving sum using movsum()

arraydiscardendpointcalculationsendpointsMATLABmovingsum

I am new to matlab and this is a code for computing moving sum from 3 consecutive numbers in matlab from Mathworks documentation. I am unable to understand what they mean by discarding endpoint calculations in the explanation(underlined ). I do not understand the significance of endpoints and discard keyword in the given documentation.If someone can explain this it would be very helpful .

Compute the three-point centered moving sum of a row vector, but discard any calculation that uses fewer than three points from the output. In other words, return only the sums computed from a full three-element window, discarding endpoint calculations.

A = [4 8 6 -1 -2 -3 -1 3 4 5];

M = movsum(A,3,'Endpoints','discard')

M = 1×8

18 13 3 -6 -6 -1 6 12

Best Answer

If you do not specify the endpoints to be discarded, the MATLAB appends zeros at both ends of the array to make them the window fit. For example, if you run

A = [4 8 6 -1 -2 -3 -1 3 4 5];
M = movsum(A,3)

then MATLAB will create matric A like this

A = [0 4 8 6 -1 -2 -3 -1 3 4 5 0];

so that window of size 3 can fit at 4 (first element) and 5 (last element)

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MATLAB: Assign moving window average if 50 % of the values in the window are within a threshold

threshold=5;%whatever you want your threshold to be
threshold2= ;%window size/2
mvavg = movmean(temp_ms, [left_window right_window],'omitnan',...
                       'Endpoints', 'discard'); 
mvsum = movsum(temp_ms<threshold, [left_window right_window],'omitnan',...
                       'Endpoints', 'discard'); 
mvavg(mvsum<threshold2)=nan;

MATLAB: How to modify a matrix to change the entries >=0 and multiply it by 5 AND to change the entries <0 and add 2 to those entries

Start with "If an entry in B is greater than or equal to zero": You can either run a loop over all elements of B or use "logical indexing":

% Linear indexing:
for k = 1:numel(B)
   if B(k) >= 0
     ...
   end
end

Or two indices for rows and columns:

for r = 1:size(B, 2)
  for c = 1:size(B, 1)
    if B(r, c) >= 0
       ...
    end
  end
end

Or "logical indexing":

index = (B >= 0);
disp(B(index))

Now try to use this to modify B. Use the mentioned terms to search in the documentation and in the internet.

Best Answer

Related Solutions

MATLAB: Assign moving window average if 50 % of the values in the window are within a threshold

MATLAB: How to modify a matrix to change the entries >=0 and multiply it by 5 AND to change the entries <0 and add 2 to those entries

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