SortBy won't order irrationals

*To*: mathgroup at smc.vnet.net*Subject*: [mg124028] SortBy won't order irrationals*From*: Chris Young <cy56 at comcast.net>*Date*: Fri, 6 Jan 2012 04:16:42 -0500 (EST)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com

Have to use N[ ] on them first. Combined with Sort's refusal to accept multiple keys, this is extremely exasperating. In[1218]:= ptsIrr = { {0, 2}, {1, Sqrt[2]}, {2, 2}, {4, 1}, {Sqrt[5], 1}, {6, 1}, {Sqrt[3], 1}, {7, 0}, {-1, 0} } Out[1218]= {{0, 2}, {1, Sqrt[2]}, {2, 2}, {4, 1}, {Sqrt[5], 1}, {6, 1}, {Sqrt[3], 1}, {7, 0}, {-1, 0}} In[1219]:= sortIrrY = SortBy[ptsIrr, #[[2]] &] Out[1219]= {{-1, 0}, {7, 0}, {4, 1}, {6, 1}, {Sqrt[3], 1}, {Sqrt[5], 1}, {0, 2}, {2, 2}, {1, Sqrt[2]}} In[1220]:= sortIrrYN = SortBy[ptsIrr // N, #[[2]] &] Out[1220]= {{-1., 0.}, {7., 0.}, {1.73205, 1.}, {2.23607, 1.}, {4., 1.}, {6., 1.}, {1., 1.41421}, {0., 2.}, {2., 2.}} In[1221]:= sortIrrYN2 = SortBy[ptsIrr, N[#[[2]]] &] Out[1221]= {{-1, 0}, {7, 0}, {4, 1}, {6, 1}, {Sqrt[3], 1}, {Sqrt[5], 1}, {1, Sqrt[2]}, {0, 2}, {2, 2}}

**Follow-Ups**:**Re: SortBy won't order irrationals***From:*DrMajorBob <btreat1@austin.rr.com>

**Re: SortBy won't order irrationals***From:*Andrzej Kozlowski <akoz@mimuw.edu.pl>