MATLAB: Creating a matrix of zeros of size of another matrice

MATLABmatricesize;

I have code , in which a matrice r as 1*100 matrice.
then It makes make
pp=zeros(1,size(r,2));
I don't know what 2 means , I know that 1 means the number of rows , but only 2 works in this comment
what is it ?
thank you

Best Answer

So zeros(a1,a2) creates a matrix of zeros with a1 rows and a2 columns, for example:
    a=zeros(2,3)
is    
    a=0 0 0
      0 0 0
So code pp=zeros(1,size(r,2)); will create matrix pp with 1 row and size(r,2) columns. As long as size(r,2 ) is the number of columns of matrix r, size of pp will be equal to size of r.
Size(r,1) is number of rows in matrix r
Size(r,2) is number of columns
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