How to reshape matrix according to the given matrix?

Hi,

Let i have 10 X 1 matrix

matrix_value indices

1 - 3

2 - 5

3 - 2

4 - 1

5 - 2

6 - 4

7 - 5

8 -1

9 - 4

10 - 3

Now I have store this in matrix of size 5 x 2 such that matrix_value of same indices will be in pairs ( in this i have taken only pairs, it may be more) . Matrix_values will be like below:

row1 4 , 8

row2 3, 5

row3 1, 10

Hope you got this, I have to create loop so that next time when i will get 20 x 1 matrix with indices, I can arrange them in (10 x 2) or any ( * x 2) pair.

Thanks and Regards

Answer 1

[Cris LaPierre]

I would use sort and reshape

% Original data
matrix_value = [3;5;2;1;2;4;5;1;4;3];
% sort the data
[tmp,I] = sort(matrix_value);
% reshape and transpose to be nx2
newInd = reshape(I,2,[])'

newInd = 5×2

4 8 3 5 1 10 6 9 2 7

newMat = reshape(tmp,2,[])'

newMat = 5×2

1 1 2 2 3 3 4 4 5 5

[SANDEEP SINGH RANA]

Thank you sir. It really helpful. In this matrix, if i have matrix_value of odd pair, then how can we write this.

% Original data

matrix_value = [3;5;2;1;2;4;5;1;2;3];

Now sorted matrix should be like this:

Matrix = 5×2

4 8

3 5 9

1 10

6

2 7

And if we can do all values in 2 column, As below.

Matrix = 5×2

4 8

3 5

9

1 10

6

2 7

[Cris LaPierre]

You cannot create a matrix in MATLAB that does not have the same number of rows in every column, and columns in every row.

[SANDEEP SINGH RANA]

Remaining empty column element can be replaced with zeros or initialized matrix using zeros(5,2), As below.

Matrix = 5×2

4 8

3 5

9 0

1 10

6 0

2 7

Only this I required is same indices matrix_value will be in pair of 2 column or it should be left alone.

[Cris LaPierre]

I guess the simplest approach would be to make sure all numbers appear an even number of times, then use the same approach as before. Set any indices greater than the length of the original vector to 0.

% original vector
matrix_value = [3;5;2;1;2;4;5;1;2;3];

% find number of times each value appears
[g,id] = groupsummary(matrix_value,matrix_value,"nnz")

g = 5×1

2 3 2 1 2

id = 5×1

1 2 3 4 5

% Append values to the bottom so all values appear an even number of times
odd = logical(rem(g,2));
matrix_value2 = [matrix_value;id(odd)];

% sort the data
[tmp,I] = sort(matrix_value2);
% reshape and transpose to be nx2
newInd = reshape(I,2,[])';
% set any indices greater than orginal length to 0
newInd(newInd>length(matrix_value)) = 0

newInd = 6×2

4 8 3 5 9 0 1 10 6 0 2 7