# How to select specific data from one matrix and place it in another

1 view (last 30 days)
stelios loizidis on 2 Nov 2020
Commented: Ameer Hamza on 2 Nov 2020
Hello,
I have the following problem. I have a large matrix A (1X960). At positions 336 I have the prices for 14 consecutive Mondays. That is, every Monday has 24 prices. Then, in the next 312 positions I have data for 13 consecutive Fridays (every Friday has 24 prices) and in the last 312 positions I have data for 13 consecutive Saturdays (every Saturday has 24 prices).
What I'm trying to do is this: In a new matrix B I want to put the data in order. That is, to enter first the 24 values ​​of Monday, then the 24 values ​​of Friday and then the 24 values ​​of Saturday. This should continue for all the data in matrix A. Your help is important !!!
Rik on 2 Nov 2020
What have you tried so far?

Ameer Hamza on 2 Nov 2020
Try this
data = 1:960;
A = reshape(data, 24, []).';
B = zeros(size(A));
B(1:3:end, :) = A(1:14, :);
B(2:3:end, :) = A(15:27, :);
B(3:3:end, :) = A(28:40, :);
B = reshape(B.', 1, [])
Ameer Hamza on 2 Nov 2020
I am glad to be of help! :)

Cris LaPierre on 2 Nov 2020
See Ch 5 of MATLAB Onramp.

dpb on 2 Nov 2020
The following can be optimized, but if I understand you want the data reordered by hour for each day, then the basic idea for any number of days and observations per day assuming every daily observation is complete set of numPerDay.
nDays=[14,13,13];
numPerDay=24;
dIx=nDays*numPerDay;
ix1=[1 cumsum(dIx(1:numel(nDays)-1))+1];
for i=1:24
B(i,:)=A(ix1);
ix1=ix1+1;
end