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}}
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