Creating matrix and then using it in another code.

I want to create a matrix in progression. I have 10000 random values of X in a spreadsheet. i want to impost it and then create a diagonal matrix in the form of

X 0 0 0

0 X 0 0

0 0 0 X

0 0 0 X

But for 10000 times for all 10000 different values of X in one run.

Basically I want to do Monte Carlo but with the elements of the matrix keeping the diagonal values same and getting 10000 different matrices and then run another code with of those 10000 values inone run and plot how it acts in a graph.

Answer 1

[Abderrahim. B]

Hi!

Not sure if I understood your question correctly, but here is a potential answer:

% Creating dummy data. in  your case use readmatrix() to import data
A = randi(10, 1000, 1) ;
B = diag(A);

Edit:

for ii = 1:length(A)
     B = diag(A(ii)*ones(4,1)) 
end

HTH

[Aniket Dutta]

What you have done is create a single matrix of 1000 x 1000 with the diagonal values of A.

what i want is 1000 different 4x4 matrix in the form of B = [A 0 0 0; 0 A 0 0; 0 0 A 0; 0 0 0 A]

basically the result should look something like

A = 1

B = [1 0 0 0; 0 1 0 0; 0 0 1 0; 0 0 0 1]

A = 3

B = [3 0 0 0; 0 3 0 0; 0 0 3 0; 0 0 0 3]

A = 10

B = [10 0 0 0; 0 10 0 0; 0 0 10 0; 0 0 0 10]

A = 9

B = [9 0 0 0; 0 9 0 0; 0 0 9 0; 0 0 0 9]

.

.

.

and i want the answer like this in one run.

Do you have any kind of code that could do this?

[Abderrahim. B]

Do you want just to print these matrices or want them in the workspace? and is it okay to use for loop?

[Aniket Dutta]

i want to use for loop

[Abderrahim. B]

Check the edit!

[Abderrahim. B]

If you want to store matrices to workspace as a struct . This struct will contain all the B matrices.

A = randi(10, 1000, 1) ;
S = struct ;

for ii = 1:length(A)
     S(ii).B = diag(A(ii)*ones(4,1)) ;
     
end

[Aniket Dutta]

Thank you.

can you also tell me how i can apply this matrix from the struct to another variable matrix to make a 6x6 matrix and create another struct in a simillar amnner

[Abderrahim. B]

Did not get very well what you wanted to say! Below assuming that you want to create 6x6 matrices from the A,and store them in a struct :

A = randi(10, 1000, 1) ;

S_four = struct ;
S_six  = struct ;

for ii = 1:length(A)
     S_four(ii).B = diag(A(ii)*ones(4,1)) ;
     S_six(ii).B = diag(A(ii)*ones(6,1)) ;
     
end

% want to access data in a field, use dot notation

B_six1 =  S_six(1).B

B_six1 = 6×6

5 0 0 0 0 0 0 5 0 0 0 0 0 0 5 0 0 0 0 0 0 5 0 0 0 0 0 0 5 0 0 0 0 0 0 5

[Aniket Dutta]

What i want to do is to make another loop to give me another set of matrices.

lets say i want to use a matrix where ii=n for which A = X

so B = [X 0 0 0; 0 X 0 0; 0 0 X 0; 0 0 0 X]

therefore my final matrix 6x6, say D should be in the form of

D = blkdiag(B(1:2,1:2), L, B(3:4,3:4), L) where say L=100.

i want this but use the values of B from the previous struct to get 10000 respective values of D.