operations on two different matrices

I need to replace the first row from a matrix A(m.m) by first row from another matrix B(n.n) with different size?

Answer 1

[Walter Roberson]

D0 j=1,8

A(1, j)=D(2,j+1)

end do

Acol = size(A,2);
A(1,:) = D(2,2:Acol+1);

vec = DD1(1,:);

A1(idx,:) = repmat(vec,numel(idx),1);

Acol = size(A,2);
vec = DD1(1,1:Acol);
A1(idx,:) = repmat(vec, numel(idx), 1);

[Mohamed Hajjaj]

Yes, it works. Thank you very much for your help.

Answer 2

[the cyclist]

Suppose ...

m = 3;
n = 4;

A = magic(m)

A = 3×3

8 1 6 3 5 7 4 9 2

B = magic(n)

B = 4×4

16 2 3 13 5 11 10 8 9 7 6 12 4 14 15 1

The first row of A is a 1x3 row vector, and the first row of B is a 1x4 row vector. What do you want the output to be? Also, what if m had been greater than n?

[Mohamed Hajjaj]

well, I want to replace the the first row of A by the elements 2 3 13 from the first row of B.

In another case, if A: n x n and B: m x m and n +2 = m want to replace A(1, :) by B(1: 2 to n-1).

[the cyclist]

Sorry, I still don't understand. Let's take a few specific cases. (The vectors represent the first row.) What should the output be in these cases?

Case 1

A = [8 1 6];
B = [16 2 3 13];

newA = [2 3 13]; % This is what you just said, so confident here.

Is the general rule that you take from the right-hand end?

Case 2

A = [16 2 3 13];
B = [8 1 6];

newA = ?; % What should it be?

Case 3

A = [30 39 48 1 10 19 28];
B = [8 1 6];

newA = ?; % What should it be?

Case 4

A = [8 1 6];
B = [30 39 48 1 10 19 28];

newA = ?; % What should it be?

I'm just trying to understand the general rule, and make sure it covers all possible cases.

[Mohamed Hajjaj]

First of all, I would like to thank you for your interesting; the next case may be represent my problem:

If we have A(8,8) and D(10,10) and we can write the following Do-Loop in Fortran:

D0 j=1,8

A(1, j)=D(2,j+1)

end do

is there a simple method to transform into Matlab?

[Mohamed Hajjaj]

Soryy, I have tried for the case of A1 and DD1 are of equal size but it did not work; I think may be becaue of A1 is complex while DD1 is real?:

vec = DD1(1,:);

A1(idx,:) = repmat(vec,numel(idx),1);

[the cyclist]

Sorry, but your last two comments are just confusing to me.

You did not respond to my questions. What are the results for Case 1, Case 2, etc?

I don't know Fortran anymore, so cannot interpret that.

Why are you suddenly introducing new variables (D, DD1, idx)? Your original question seemed very simple, about filling in the first row of a matrix A, from the first row of a matrix B. It seems to be getting more and more complicated with every comment.

[Mohamed Hajjaj]

The first case is the nearest one to my problem.The symbols D, DD1, ...are matrices, but I'm sorry about any confusion. Would you please help me for the first case?