Re: select 1st column element based on criteria in 2nd column in mathematica

*To*: mathgroup at smc.vnet.net*Subject*: [mg124179] Re: select 1st column element based on criteria in 2nd column in mathematica*From*: Murray Eisenberg <murray at math.umass.edu>*Date*: Wed, 11 Jan 2012 17:23:02 -0500 (EST)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com

You cannot directly select from a "table", as there is no such object in Mathematica. You want to select from a list of 2-element lists. (You may _display_ such a list of lists in Table form, but such a display is not an object upon which you'd want to operate.) So do it like this (among other ways): pairs = {{1,3}, {2,4}, {3,6}, {4,1}, {5,3}, {6,2}, {7,5}, {8,2}}; First /@ Select[pairs, Last[#] > 3 &] The Select function pulls out those pairs that satisfy your condition; the condition is specified by the "pure function" that's the 2nd argument to Select. Finally, mapping First (First /@ ...) onto the result gives the first member of each pair selected. On 1/11/12 4:18 AM, Hani wrote: > hello, I have a question. > > Suppose I have a table with two columns like this: > > 1 3 > 2 4 > 3 6 > 4 1 > 5 3 > 6 2 > 7 5 > 8 2 > > I want to select elements of the 1st column which its corresponding 2nd > column elements are bigger than 3. so, the result should be {2,3,7}. How to > implement that in mathematica? Thanx a lot > -- Murray Eisenberg murray at math.umass.edu Mathematics & Statistics Dept. Lederle Graduate Research Tower phone 413 549-1020 (H) University of Massachusetts 413 545-2859 (W) 710 North Pleasant Street fax 413 545-1801 Amherst, MA 01003-9305