Re: Need to reduce 2 lists so that only {x,y} pairs with same x remain

• To: mathgroup at smc.vnet.net
• Subject: [mg24189] Re: Need to reduce 2 lists so that only {x,y} pairs with same x remain
• From: dkeith at sarif.com
• Date: Wed, 28 Jun 2000 22:51:09 -0400 (EDT)
• References: <8jc73k\$dg3@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```Hi Chuck,

This function accepts the two lists and returns a list of two lists
whose x values are contained in the set intersection of the x values of
the two lists.

commonX[list1_, list2_] := Select[#, MemberQ[Intersection[list1
[[All,1]], list2[[All, 1]]],
#[[1]]] &] & /@ {list1, list2}

In article <8jc73k\$dg3 at smc.vnet.net>,
materialsscientist at my-deja.com wrote:
> Hello,
>
> I have 2 lists of data:
>
> for example
> data1={{1,1},{1.5,1.5},{2,2},{3,3},{4,4},{5,5}}
>
> data2={{1,2},{2,3},{3,4},{4,5},{6,7},{7,8}}
>
> I want to do a point by point comparision, so I
> need to reduce both data1 and data2 so that
> common x data in the {x,y} pairs for each list
> remain.
>
> Thus the lists should look like this:
>
> data1={{1,1},{2,2},{3,3},{4,4}}
> data2={{1,2},{2,3},{3,4},{4,5}}
>
> What function(s) would to something like this?
>
> Thanks,
>
> Chuck
>
> Sent via Deja.com http://www.deja.com/