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I'm working on some pet project and I have a very large list of {x,y} pairs. I want to make a new list containing all {x,y} pairs where x is, let's say, even (I actually need something more complicated, but I assume same principle will apply). I just don't get how I'm even supposed to do it, Select doesn't work (or can't make it work) on pairs. I've read Select documentation but it seems I'm missing something essential.

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marked as duplicate by Yves Klett, rm -rf Jan 2 at 15:42

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Welcome to Mathematica SE. What you describe is so basic to Mathematica, it's clear you would benefit from examining the examples under Cases, Select. Also a tutorial on replacement and Rule would be helpful. –  David Carraher Jan 2 at 15:09

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