How to make empty array of specific size?

I used A = ClassName.empty(sz1,...,szN) or A = ClassName.empty(sizeVector) syntax :

a=ClassName.empty(2,2)

but I got this error:

Undefined variable "ClassName" or class "ClassName.empty".

[Walter Roberson]

You would have to substitute the name of the class for ClassName

[Zeynab Mousavikhamene]

@Walter Roberson I changed to a.empty(2,2). But now a=0 and isempty(a)=0. Why? It should be ''empty'', not zero

Answer 1

[Walter Roberson]

https://www.mathworks.com/matlabcentral/fileexchange/31362-uninit-create-an-uninitialized-variable-like-zeros-but-faster

Answer 2

[Steven Lord]

Replace ClassName with the name of the class for which you want to create the empty array.

But in order to use the empty method, the size of the array you want to create must be 0 in at least one of its dimensions. You can't, for example, have a 2-by-2 empty array. If you want to make a double 2-by-2 array, use zeros, ones, rand, eye, etc.

x = zeros(2); % 2-by-2 double array filled with 0's
y = ones(2, 'single'); % 2-by-2 single array filled with 1's
z = int8.empty(2, 2, 0) % 2-by-2-by-0 int8 array

[Zeynab Mousavikhamene]

@ Steven Lord Thanks but as I said in the question, for some reason I dont want to create with numbers like zero or one and it seems matlab does not have that capability.

[Steven Lord]

If the array has at least one element, those elements must have a value. Let's say you created your "empty" 2-by-2 matrix a. What specifically do you want the value of q to be after running the following line of code?

q = a(1, 1);

Answer 3

[Linnéa Haugen]

I found another solution that starts out empty. i also wanted to create an empty array, with 2 columns but of unknown length.

arr = [[], []];

if ..

else

arr(end+1,1) = a;

end

if..

arr(end,2) = b;

end

a and b are changing in a for loop and i only need to save some values. i'm finding peaks and if i find one i save to location (a) and change the hight by the amount (b).

I only have an interest in the values i change, and i don't know how many i'll change in advance.

Answer 4

[HAG]

To create an empty array of any length, use zeros function

zeros(4,0)

ans =

  4×0 empty double matrix