Adding a row and column is a matrix

I intializes a zero matrix [#bus,#bus] (name it z). And would like to increase a row and a column and do that in a for loop (name it zmod).

Moreover, the new row should be equal to the transposed of the new column.

How can I do this?

Answer 1

[William Rose]

@Fatima Yusuf,

This code creates a square array of zeros. Then it adds a row and a column which are transpose of eachother, in a for loop, until it reaches the FinalSize.

%augmentArray.m
%WCRose 20210329

clear;

InitSize=3;
FinalSize=5;
z=zeros(InitSize);
zmod=z;
for i=InitSize:FinalSize-1
    a=rand(i,1);    %column to add
    b=[a',rand(1)]; %row to add
    zmod=[zmod,a;b];
end
disp(zmod)

Try it.

[Fatima Yusuf]

@William Rose

what is "rand"?

[William Rose]

@Fatima Yusuf,

rand(i,1) generates an array of random numbers, with i rows and 1 column. rand(1) generates a single random number. I used rand to generate some numbers, so that you could tell, in the results, that The dded rows were the transpose of the added columns. If I had just added zeros or ones to th array, you might have doubted that the rows and columns were really transpose of each other.

[Fatima Yusuf]

What if I added a row and col with zeros value and would like to change the last element of the matrix (final size,final size)

[William Rose]

@Fatima Yusuf,

Then you could change the for loop to the following:

for i=InitSize:FinalSize-1
    a=zeros(i,1);    %column to add
    b=zeros(1,i+1);  %row to add
    zmod=[zmod,a;b];
end

or you could do

for i=InitSize:FinalSize-1
    zmod=[zmod,zeros(i,1);zeros(1,i+1)];
end

If that is what you want to do, then the script above seems unnecessary. You could replace the whole script with the line

zmod=zeros(FinalSize);

which produces the same result as the for loop.