How to compare two vector with different dimension

Hello, I have two vectors

x1 = [1;2;4;7;8];
y1 = [2;5;8;6;1];

which are coordinates of all zero and non zero values of a matrix. And then

x2=[2;8;7]
y2=[6;1;2]

are the coordinates of just the non-zero values. Then how to get the coordinates of zero values? Please help.

[Geoff Hayes]

Boni_PI - so if a coordinate is in (x2,y2) and in (x1,y1) then it is the coordinate of a non-zero value and so should be ignored. If the coordinate is in (x1,y1) and not in (x2,y2) then it is the coordinate of a zero value which you are interested in. Is that correct?

[Star Strider]

Something about this does not make sense. The matrix must be at least (8x8), so assuming it is just that, this:

Ln = sub2ind([8 8], x2, y2);
A = NaN(8);
A(Ln) = 42
Lz = sub2ind([8 8], x1, y1);
A(Lz) = 0

produces:

A =
   NaN     0   NaN   NaN   NaN   NaN   NaN   NaN
   NaN   NaN   NaN   NaN     0    42   NaN   NaN
   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN
   NaN   NaN   NaN   NaN   NaN   NaN   NaN     0
   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN
   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN
   NaN    42   NaN   NaN   NaN     0   NaN   NaN
     0   NaN   NaN   NaN   NaN   NaN   NaN   NaN

[Boni_Pl]

Geoff Hayes yes your concept is correct. But How to write the code to separate zero and non zero coordinates from x1 & y1 if the dimension is 50x1. and x2 & y2 vector's dimension is 29x1.

[the cyclist]

Boni_PI, I edited your question just a bit, using the CODE button to format your vectors.

[Adam]

What are the other options than 'zero or non-zero' in your matrix?! surely that set should cover every element of the matrix?

Answer 1

[Jos (10584)]

I assume the elements of x and y are linked? Why is the first element of (x2,y2) than not in the list of coordinaties (x1,y1)? I assume this is a mistake.

If I were you, I would link the coordinates explicitly, as rows of a N-by-2 array, allowing to use SETDIFF:

xy_all = [x1(:) y1(:)] 
xy_nonzero = [x2(:) y2(:)] 
xy_zero = setdiff(xy_nonzero, xy_all, 'rows')