how to extract n elements from a vector and store them in a matrix

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Hi,
I have a matrix with 3 variables:
a = [3 6 0 3 8 4 9 1 2 4 9 3 2 5 7 0 1 2.....]
b = [5 6 5 3 1 3 8 2 2 3 5 7 1 2 6 1 6 7.....]
c = [0 0 0 0 1 0 0 0 0 0 0 0 1 0 0 0 0 0.......]
I want to write a for loop that every time that c == 1 goes to the corresponding position of a and b, cuts 5 elements from each vector and stores them in two different matrices that would look something like this:
matrix a
a1 8 4 9 1 2
a2 2 5 7 0 1
a3 ....
matrix b
b1 1 3 8 2 2
b2 1 2 6 1 6
b3 .....
any idea on how to do it?

Accepted Answer

Image Analyst
Image Analyst on 20 Jun 2022
Try this:
a = [3 6 0 3 8 4 9 1 2 4 9 3 2 5 7 0 1 2];
b = [5 6 5 3 1 3 8 2 2 3 5 7 1 2 6 1 6 7];
c = [0 0 0 0 1 0 0 0 0 0 0 0 1 0 0 0 0 0];
locations1 = find(c == 1);
aMatrix = zeros(numel(locations1), 5);
bMatrix = zeros(numel(locations1), 5);
for row = 1 : numel(locations1)
thisIndex = locations1(row);
aMatrix(row, :) = a(thisIndex : thisIndex + 4);
bMatrix(row, :) = b(thisIndex : thisIndex + 4);
end
aMatrix % Show in command window.
aMatrix = 2×5
8 4 9 1 2 2 5 7 0 1
bMatrix % Show in command window.
bMatrix = 2×5
1 3 8 2 2 1 2 6 1 6
and this:

More Answers (2)

Fangjun Jiang
Fangjun Jiang on 20 Jun 2022
a = [3 6 0 3 8 4 9 1 2 4 9 3 2 5 7 0 1 2];
b = [5 6 5 3 1 3 8 2 2 3 5 7 1 2 6 1 6 7];
c = [0 0 0 0 1 0 0 0 0 0 0 0 1 0 0 0 0 0];
in1=find(c);
in2=in1'+[0:4];
NewA=a(in2)
NewA = 2×5
8 4 9 1 2 2 5 7 0 1
NewB=b(in2)
NewB = 2×5
1 3 8 2 2 1 2 6 1 6

Hernia Baby
Hernia Baby on 20 Jun 2022
Edited: Hernia Baby on 20 Jun 2022
a = [3 6 0 3 8 4 9 1 2 4 9 3 2 5 7 0 1 2];
b = [5 6 5 3 1 3 8 2 2 3 5 7 1 2 6 1 6 7];
c = [0 0 0 0 1 0 0 0 0 0 0 0 1 0 0 0 0 0];
temp = cumsum(c)
temp = 1×18
0 0 0 0 1 1 1 1 1 1 1 1 2 2 2 2 2 2
for ii = 1:max(temp)
ta = a;
tb = b;
ta(temp~=ii)=[];
tb(temp~=ii)=[];
A{ii,1}=ta(1:5);
B{ii,1}=tb(1:5);
end
A=cell2mat(A)
A = 2×5
8 4 9 1 2 2 5 7 0 1
B=cell2mat(B)
B = 2×5
1 3 8 2 2 1 2 6 1 6

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