# Calculate mean of a matrix with different indices

4 views (last 30 days)
Dion Theunissen on 17 Mar 2021
Commented: Bjorn Gustavsson on 17 Mar 2021
Hi,
I have a loop as below.
RCAr = []
for k = 1:length(RCA);
...
...
afstand = thisData(1:a,1);
lengte = size(dx);
lengte = round(lengte);
for i = 1:lengte-1
P1 = [dx(i), dy(i), dz(i)];
P2 = [dx(i+1), dy(i+1), dz(i+1)];
distance(i) = norm(P1 - P2);
end
distance2(:,1) = distance;
RCAr(:,k) = angleradian2; %this point is not working
hold on
end
I want to make a matrix of k columns with all the angleradians. But the indices of angleradian does not have the same length. How can I fix this?
I want to calculate the mean of each row and stdev of each row of that matrix.

Bjorn Gustavsson on 17 Mar 2021
So you effectively have different number of dx for each k? If so I'd do this something like this:
angleradian2 = nan([MaxNrRows,MaxNrCols]); % pre-allocate a nan-array with correct size
RCAr = angleradia2; % just make place for this one too
distance = RCAr; % and this one,
afstand = RCAr; % and this one...
for i1 = 1:length(RCA); % Changed k to i1 to get identifying label on loop-variable
...
...
afstand(i1,1:a) = thisData(1:a,1);
lengte = size(dx,1); % or 2 instead of 1, size returns a 2 (at least) element array with
% [sz1, sz2, ... szN] since you use this as an upper
% bound of your iteration it should be a scalar!
lengte = round(lengte);
for i2 = 1:lengte-1 % changed i to i2 for same reason as above AND keep i free for complex unit
P1 = [dx(i2), dy(i2), dz(i2)];
P2 = [dx(i2+1), dy(i2+1), dz(i2+1)];
distance(i1,i2) = norm(P1 - P2);
end
RCAr(i1,:) = angleradian2(i1,:); %this point is not working
hold on
end
HTH
Bjorn Gustavsson on 17 Mar 2021
Great!

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