Using Select
- To: mathgroup at smc.vnet.net
- Subject: [mg97371] Using Select
- From: "Karsten W." <Karsten.G.Weinert at googlemail.com>
- Date: Thu, 12 Mar 2009 02:16:40 -0500 (EST)
Hello, here is a problem I have solved but I am not happy with the method I have a data matrix DATA, a list of m ordered n-tuples. I run a function on the data matrix which returns a list DATAEVAL with m elements. The i-th element of this list corresponds to the i-th tuple of the data matrix. I think of this DATAEVAL list as an additional column of the data matrix. Now I am only interested in those tuples of the data matrix, where the corresponding DATAEVAL list has a value greater than zero. My current approach is the following: I add the DATAEVAL list to the data matrix and call Select afterwards: data = Import[...]; dataEval = f[data, ...]; filteredData = Select[Transpose[Join[Transpose[data], {dataEval}] ], Last[#] > 0 &]; This works. However, calling Transpose two times seems not to be the most efficient way to solve the problem. As a newbie to Mathematica (and functional programming), I wonder if you can point me to a simpler solution? Kind regards, Karsten.
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