Sum elements in a list with conditions
- To: mathgroup at smc.vnet.net
- Subject: [mg128422] Sum elements in a list with conditions
- From: Guillermo Sanchez <guillermo.sanchez at hotmail.com>
- Date: Thu, 18 Oct 2012 02:36:46 -0400 (EDT)
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I have a list of sublist of pairs. I wish sum the second elements of the sublists when the first elements are equals Example: Int[]:={{1, a}, {2, b}, {1, c}, {2, d}, {2, e}, {3, f}} I hope Out[]:= {{1, a + c}, {2, b + c + e}, {3, f}} I can do it as is it is shown below but could any body find and easier solution. list1 = {{1, a}, {2, b}, {1, c}, {2, d}, {2, e}, {3, f}}; list2 = GatherBy[list1, First]; {l1, l2} = Transpose[Plus @@@ GatherBy[list, First]]; Transpose[{l1/Length /@ list2 , l2}]
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- Re: Sum elements in a list with conditions
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