AutoCAD 2013 :: Array Editing To Fill Shape

I was trying to figure out how to edit an array to either remove all the array objects outside of a shape or to fill in a shape with  objects. 

For example, I created a rectangular array of dots and want to remove the dots such that it makes a circle (or triangle if that's possible?). There are reasons that I can't use the polar array to make the circle because I need certain parameters that really I can't replicate. Also, selecting each point is too tedious and really not efficient (though it could be done eventually, but I don't want to waste a ton of time).