If you have a list with a lot of zeros and want to get rid of them you can do something like this:
# 0, 42
foo:=remove(`=`,foo,0); # removes x in foo with x=0
# 7, 42
If you are doing this numerically, you might want to get rid of small
values instead of just the zeros. In that case you could do something like:
From your code, it looks like points4 is a sequence of pairs [x,y].
If you want to filter just based on the x value, you could do:
Hope that helps.