I have a list of data, I tried to SortBy it in two equivalent way, but the result is different.
The data variable is something like
{{"2018-05-14", 6.184292`, 6.717337`}, {"2019-01-10", -3.931206`,
0.992981`}, {"2018-09-03", 10.06036`, 2.15906`},...}
First way, I sort it like this
SortBy[data, #[[2]] &][[;; , -1]][[-4 ;; -1]]
it gives
{2.15906, 1.86386, 4.42245, 1.93505}
Second way, I sort it like this
Transpose[SortBy[data[[;; , {2, 3}]], First]][[2]][[-4 ;; -1]]
I naively thought this should give the same result as the first way. But it gives
{1.86386, 2.15906, 4.42245, 1.93505}
I can not figure out why, a limited test seems to show that the first column of string affect the sorting result. But I really don't know why. Is it a bug?
Is there some workaround to get stable sorting result with SortBy?
PS:
the full data variable is as below
data = {{"2018-05-14", 6.184292`,
6.717337`}, {"2019-01-10", -3.931206`, 0.992981`}, {"2018-09-03",
10.06036`, 2.15906`}, {"2017-04-13", 10.00603`,
5.872783`}, {"2017-06-23", -3.278692`, 3.102502`}, {"2019-03-01",
10.`, 11.753364`}, {"2017-03-23", 2.001785`,
12.764118`}, {"2017-05-17", 3.229816`,
2.436859`}, {"2019-02-27", -5.761638`, 10.630857`}, {"2018-11-19",
2.238807`, 7.370008`}, {"2018-01-25", -4.185268`,
8.715547`}, {"2019-02-14", 9.981172`, 1.042997`}, {"2017-03-29",
10.00949`, 5.63856`}, {"2017-03-17", 10.00622`,
4.482422`}, {"2018-08-09", 9.015448`,
15.249212`}, {"2018-11-07", -6.416273`, 3.560157`}, {"2018-01-19",
6.864568`, 9.58189`}, {"2019-01-16", -4.835393`,
2.745814`}, {"2017-01-13", 10.01484`,
7.819988`}, {"2017-12-29", -4.930658`, 2.331498`}, {"2017-11-14",
10.02825`, 3.705003`}, {"2018-11-01", 2.84006`,
5.798435`}, {"2018-10-18", -9.730444`, 6.403442`}, {"2018-11-19",
9.99044`, 4.594504`}, {"2017-04-11", 9.989251`,
8.665032`}, {"2018-01-24", 9.973293`, 4.113164`}, {"2018-05-31",
9.979642`, 5.436269`}, {"2017-12-18", -1.983477`,
1.464409`}, {"2018-07-27", -8.452954`, 1.244757`}, {"2017-05-31",
10.01268`, 13.419636`}, {"2017-08-29", 9.999996`,
12.275278`}, {"2018-07-10", -2.012577`, 1.988242`}, {"2018-04-12",
1.820249`, 5.015844`}, {"2017-12-13", 9.981937`,
14.314185`}, {"2017-03-03", 10.00437`,
12.55615`}, {"2017-10-18", -7.613326`, 11.405841`}, {"2018-09-14",
9.611231`, 11.38485`}, {"2018-01-08", 10.00422`,
7.481106`}, {"2018-03-13", 0.`, 2.951733`}, {"2018-07-30",
1.284959`, 13.011311`}, {"2018-10-08", -2.857145`,
2.654354`}, {"2018-07-03", 0.74074`, 1.967703`}, {"2018-11-16",
10.00667`, 4.859302`}, {"2018-02-22", 3.131317`,
3.019479`}, {"2017-02-13", 0.285714`, 2.303895`}, {"2018-09-14",
10.07194`, 1.93505`}, {"2017-03-13", -2.458607`,
6.74963`}, {"2019-02-14", -1.994792`,
7.38112`}, {"2017-08-29", -1.603944`,
12.610766`}, {"2017-07-18", -0.042311`, 12.598572`}, {"2017-09-25",
9.984406`, 3.539927`}, {"2018-08-21", -0.038359`,
4.686513`}, {"2017-05-03", 7.805756`, 10.247516`}, {"2019-01-25",
9.987517`, 2.061129`}, {"2017-04-07", 10.02865`,
9.404674`}, {"2019-02-25", 9.95608`, 1.513823`}, {"2019-01-07",
10.06036`, 1.863862`}, {"2019-02-26", 9.302326`,
4.515664`}, {"2018-01-24", 9.986224`,
9.208368`}, {"2018-11-12", -2.688811`, 4.733748`}, {"2017-04-26",
10.00693`, 6.822327`}, {"2019-01-08", -3.516175`,
2.578293`}, {"2018-05-16", 9.999996`, 6.363988`}, {"2018-03-14",
5.83941`, 3.25484`}, {"2017-03-03", -3.935598`,
10.438454`}, {"2018-05-16", 9.994114`,
3.888683`}, {"2018-10-11", -4.590159`, 5.272433`}, {"2017-02-15",
9.99465`, 22.858054`}, {"2018-03-06", 0.906059`,
17.653249`}, {"2018-06-25", 9.960545`, 5.661866`}, {"2018-11-16",
1.76057`, 1.704593`}, {"2018-11-08", 0.480257`,
3.426226`}, {"2019-01-08", 10.01789`,
2.411736`}, {"2018-03-13", -2.691887`,
4.517372`}, {"2017-06-19", -1.841573`, 1042.81686`}, {"2017-08-09",
0.619013`, 6.911994`}, {"2018-11-09", 10.`,
1.827005`}, {"2019-02-27", 5.109066`, 7.227035`}, {"2017-11-08",
0.639726`, 2.921231`}, {"2018-02-23", 8.354053`,
4.745265`}, {"2018-09-12", 10.01032`, 4.207602`}, {"2018-07-04",
9.644977`, 15.399009`}, {"2018-10-23", -0.913241`,
1.038415`}, {"2017-01-09", 9.992285`,
13.255343`}, {"2017-04-13", -2.114163`, 3.245738`}, {"2017-04-10",
9.981172`, 3.618146`}, {"2018-11-20", -3.286393`,
1.947669`}, {"2018-08-14", -8.880456`,
11.656775`}, {"2019-02-26", -3.758057`, 5.712208`}, {"2017-09-20",
9.980683`, 7.426913`}, {"2019-02-12", 3.549062`,
2.218405`}, {"2018-02-26", 6.195124`, 3.583551`}, {"2018-04-25",
9.998705`, 10.206493`}, {"2018-08-06", 10.07025`,
4.422451`}, {"2017-02-07", -0.06693`, 8.167308`}, {"2017-09-19",
10.00868`, 12.952418`}, {"2018-08-31", 7.233498`,
7.145747`}, {"2018-04-25", 0.940438`,
8.010683`}, {"2017-01-19", -0.53545`, 15.877556`}, {"2018-02-13",
3.758292`, 5.08243`}, {"2017-01-04", 9.974427`,
2.762563`}, {"2018-06-19", 9.956711`, 3.869365`}, {"2018-04-09",
1.737808`, 22.755046`}, {"2017-07-12", 2.594803`,
3.235668`}, {"2019-01-03", 10.01632`, 3.677325`}, {"2019-02-12",
2.38095`, 1.796339`}, {"2017-02-27", 9.974427`,
8.576878`}, {"2017-01-17", 4.350225`, 2.464616`}, {"2018-03-21",
7.066045`, 1.714317`}, {"2018-05-31", 0.`,
2.337773`}, {"2017-10-25", 9.99025`, 7.488821`}, {"2017-05-12",
9.980425`, 6.785923`}, {"2017-01-17", 10.01296`,
8.248838`}, {"2018-08-10", 0.`, 4.274576`}, {"2017-08-31",
0.23113`, 2.438556`}, {"2018-06-12", 4.208693`,
4.737961`}, {"2018-11-22", 9.999997`, 1.924548`}, {"2017-04-28",
10.00419`, 10.937031`}, {"2017-08-07", 10.0051`,
7.340555`}, {"2018-05-21", 3.415557`, 1.340161`}}
