extracting matrix row whose element which satisfy equation of a cirlce

I have a nx2 matrix. Each row is actually a coordinate point. I have a coordinate of center of a circle and its radius. I want to build a matrix that only contains those row of nx2 matrix whose 1st and 2nd element lie inside or on the given circle. Any hints?

Answer 1

[Guillaume]

What's the difficulty?

%points: nx2 matrix of points
%centre: 1x2 vector of circle centre
%radius: radius of circle
isincircle = sum((points - centre) .^2, 2) <= radius .^ 2;   %only works in R2016b
incirclepoints = points(isincircle, :)

If < R2016b,

isincircle = sum(bsxfun(@minus, points, centre) .^2, 2) <= radius .^ 2;