Filter data for quiver

I can't find an elegant way to plot every fourth value from my 201x301 matrix by quiver function. I have tried to make the undesired points zero but it leaves the dots, plus the cycle was quite long.

So how can I refer to particular values from the matrix???

Answer 1

[the cyclist]

Try making the undesired points NaN rather than zero.

Answer 2

[the cyclist]

If M is your matrix, then you could try plotting

>> M2 = M(1:4:end,1:4:end);

to get every fourth point in each dimension.

[ocean motion]

Thank you, but NaN I've tried myself and it didnt help. And about 2nd suggestion...you see..the point is to keep the initial size of the matrix because it's a map. I plot it as quiver(lon,lan,U,V) so if I use U(1:4:end,1:4:end) or something similar it can't plot it because the dimensions don't agree, so important is to keep the whole field but leave only chosen points with values.

[the cyclist]

Can't you apply the same concept to each of lon,lan,U,V to get the dimensions to agree?