2d array in matlab

Question

Rakesh Singh 2014-9-20

编辑： dpb 2014-9-21

how to declare 2d array in matlab

Answer 1

dpb 2014-9-20

Matlab does silent automagic allocation -- just assign

z=zeros(2); % is a 2x2 array

See "Getting Started" section in the documentation and work thru the examples to get an idea on "how Matlab works.

Image Analyst 2014-9-20

编辑：Image Analyst 2014-9-20

A neat trick is that you can expand an existing array or scalar by setting the last value to something. For example:

m=5; % m is a scalar
m(10,20) = 9;

m is now a 10 by 20 array of zeros except for the two (1,1) and (10,20) elements which equal 5 and 9 respectively.

You can also preallocate cell arrays with the cell() function and structure arrays with the struct() function.

dpb 2014-9-20

编辑：dpb 2014-9-21

...can expand an existing array or scalar by setting the last value to something.

I was just coming back to add that in, IA... :)

But, I'll note for the OP one doesn't have to add to an existing variable, same thing works to create the array; ie,

m(10,20)=9;

as the first statement will leave the array w/ just the one "9" at location 10,10, all else is zeros. It's functionally equivalent to

m=zeros(10,20);
m(end,end)=9;

where I've deliberately used the alternate functional indexing reference end as a tutorial device as well... :)