# How to position groups of matrices inside a bigger matrix

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Feliciano Döring on 30 Apr 2018
I have a program in which I have some matrices of varying size that runs through a piece of code, for the current moment i only have two matrices. What i want to know is how would i place the matrices 'M' in a bigger matrix of zeros in a way that the values always stay in the diagonal and the rest of the matrices are zeros. So, for example if a have two matrices with size 4x4 the matrix would be a 8x8 matrix with [1:4,1:4] and [5:8,5:8] being values and the rest zeros. I want to do it in a way that i can do it for n-matrices. Here is the code i use.
for iter=1:2
D=Stations{iter};
n=length(D);
c=[0;0;0;0];
rowvector=ones(1,n);
dt0=rowvector
dn=sqrt((D(1,:)-m0(2)).^2+(D(2,:)-m0(3)).^2+(D(3,:)-m0(4)).^2);
dtx = -(D(1,:)-m0(2))./(v.*dn);
dty = -(D(2,:)-m0(3))./(v.*dn);
dtz = -(D(3,:)-m0(4))./(v.*dn);
M=[dt0; dtx; dty; dtz];
end
'Stations' is a cell array i use to store the different matrices

Bob Nbob on 30 Apr 2018
Does the code work? If not what kind of errors do you get?
Will your matrices always be square?
Feliciano Döring on 1 May 2018
The code works fine, The matrices will have varying size and dont always have to be square

Siyu Guo on 2 May 2018
blkdiag function is the tool you are looking for. Help it in MATLAB. Note you can use a loop within which the function is called iteratively to cope with n sub-matrices.

#### 1 Comment

Feliciano Döring on 2 May 2018
Thanks! that is what i was looking for!