# Problem in sorting the elements of a complex column vetor in descending order.

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Commented: 奥 刘 on 16 Nov 2021
I am trying to sort the elements of a complex column vetor in descending order. The vector V is,
0.00192283028876372 + 2.81043109217511e-19i
0.00190176141109370 + 2.84699448762080e-19i
0.00147928037481547 - 2.74849838261212e-20i
0.00142769822781175 + 5.39004850343165e-20i
0.00117784972186107 + 2.08922253853130e-19i
0.00107796253204560 - 4.70645642035523e-20i
0.000800293022988111 + 1.22052572461947e-20i
0.000269899528923458 - 6.15654463989809e-20i
6.30592283269993e-05 - 7.50552502780072e-20i
2.23684164933882e-05 + 4.04939694038624e-21i
2.20073577954736e-05 - 5.80181618012595e-21i
1.95849840201760e-05 + 1.48445834874224e-20i
1.71925856406516e-05 - 1.15719050036467e-20i
1.28038961421133e-05 + 7.36148671834500e-20i
8.73059513582096e-06 + 1.23064435626381e-20i
6.28618594970652e-06 - 5.04267327744353e-20i
6.99991469893008e-08 - 1.02450891500650e-20i
2.80343931756963e-08 + 1.23048032017686e-20i
4.29713831923512e-09 + 3.73908633968205e-21i
2.28802604174547e-09 + 1.73500648980058e-20i
3.50507467296844e-10 - 1.10159115820306e-21i
7.32973689738923e-11 - 4.65099992985255e-21i
2.07808170074765e-11 - 2.84966374048803e-22i
4.68510672896002e-12 - 2.29503200085301e-21i
2.99051403313190e-12 + 3.62505072381834e-21i
1.32399364803625e-12 - 4.30261778360293e-21i
6.07212915777181e-13 + 2.79063028387683e-22i
1.23086553364893e-13 + 8.26560004261648e-21i
1.72392520759381e-14 + 1.86019192086409e-21i
1.01989680354965e-14 + 3.46136359467220e-21i
-8.05918955245067e-21 + 8.23317408693105e-22i
1.36822909718840e-15 - 1.33221528989010e-21i
I code as below,
% sort the variances in decreasing order
[junk, rindices] = sort(-1*V);
% V1=[2;6;4;3;1;8];
% [junk1, rindices1] = sort(-1*V1);
V = V(rindices);
However, after sorting, V became,
-8.05918955245067e-21 + 8.23317408693105e-22i
1.36822909718840e-15 - 1.33221528989010e-21i
1.01989680354965e-14 + 3.46136359467220e-21i
1.72392520759381e-14 + 1.86019192086409e-21i
1.23086553364893e-13 + 8.26560004261648e-21i
6.07212915777181e-13 + 2.79063028387683e-22i
1.32399364803625e-12 - 4.30261778360293e-21i
2.99051403313190e-12 + 3.62505072381834e-21i
4.68510672896002e-12 - 2.29503200085301e-21i
2.07808170074765e-11 - 2.84966374048803e-22i
7.32973689738923e-11 - 4.65099992985255e-21i
3.50507467296844e-10 - 1.10159115820306e-21i
2.28802604174547e-09 + 1.73500648980058e-20i
4.29713831923512e-09 + 3.73908633968205e-21i
2.80343931756963e-08 + 1.23048032017686e-20i
6.99991469893008e-08 - 1.02450891500650e-20i
6.28618594970652e-06 - 5.04267327744353e-20i
8.73059513582096e-06 + 1.23064435626381e-20i
1.28038961421133e-05 + 7.36148671834500e-20i
1.71925856406516e-05 - 1.15719050036467e-20i
1.95849840201760e-05 + 1.48445834874224e-20i
2.20073577954736e-05 - 5.80181618012595e-21i
2.23684164933882e-05 + 4.04939694038624e-21i
6.30592283269993e-05 - 7.50552502780072e-20i
0.000269899528923458 - 6.15654463989809e-20i
0.000800293022988111 + 1.22052572461947e-20i
0.00107796253204560 - 4.70645642035523e-20i
0.00117784972186107 + 2.08922253853130e-19i
0.00142769822781175 + 5.39004850343165e-20i
0.00147928037481547 - 2.74849838261212e-20i
0.00190176141109370 + 2.84699448762080e-19i
0.00192283028876372 + 2.81043109217511e-19i
which is defintely not in descending order.
I also tried on positive real numbers,
V1=[2;6;4;3;1;8];
[junk1, rindices1] = sort(-1*V1);
and the consequence is correct.
I don't know why the sorting of the complex numbers seems wrong.

Cris LaPierre on 15 Nov 2021
Edited: Cris LaPierre on 15 Nov 2021
Just specify 'descend' for your sort order.
format longE
V=[0.00192283028876372 + 2.81043109217511e-19i
0.00190176141109370 + 2.84699448762080e-19i
0.00147928037481547 - 2.74849838261212e-20i
0.00142769822781175 + 5.39004850343165e-20i
0.00117784972186107 + 2.08922253853130e-19i
0.00107796253204560 - 4.70645642035523e-20i
0.000800293022988111 + 1.22052572461947e-20i
0.000269899528923458 - 6.15654463989809e-20i
6.30592283269993e-05 - 7.50552502780072e-20i
2.23684164933882e-05 + 4.04939694038624e-21i
2.20073577954736e-05 - 5.80181618012595e-21i
1.95849840201760e-05 + 1.48445834874224e-20i
1.71925856406516e-05 - 1.15719050036467e-20i
1.28038961421133e-05 + 7.36148671834500e-20i
8.73059513582096e-06 + 1.23064435626381e-20i
6.28618594970652e-06 - 5.04267327744353e-20i
6.99991469893008e-08 - 1.02450891500650e-20i
2.80343931756963e-08 + 1.23048032017686e-20i
4.29713831923512e-09 + 3.73908633968205e-21i
2.28802604174547e-09 + 1.73500648980058e-20i
3.50507467296844e-10 - 1.10159115820306e-21i
7.32973689738923e-11 - 4.65099992985255e-21i
2.07808170074765e-11 - 2.84966374048803e-22i
4.68510672896002e-12 - 2.29503200085301e-21i
2.99051403313190e-12 + 3.62505072381834e-21i
1.32399364803625e-12 - 4.30261778360293e-21i
6.07212915777181e-13 + 2.79063028387683e-22i
1.23086553364893e-13 + 8.26560004261648e-21i
1.72392520759381e-14 + 1.86019192086409e-21i
1.01989680354965e-14 + 3.46136359467220e-21i
-8.05918955245067e-21 + 8.23317408693105e-22i
1.36822909718840e-15 - 1.33221528989010e-21i];
newV = sort(V,'descend')
newV =
1.922830288763720e-03 + 2.810431092175110e-19i 1.901761411093700e-03 + 2.846994487620800e-19i 1.479280374815470e-03 - 2.748498382612120e-20i 1.427698227811750e-03 + 5.390048503431650e-20i 1.177849721861070e-03 + 2.089222538531300e-19i 1.077962532045600e-03 - 4.706456420355230e-20i 8.002930229881110e-04 + 1.220525724619470e-20i 2.698995289234580e-04 - 6.156544639898089e-20i 6.305922832699930e-05 - 7.505525027800721e-20i 2.236841649338820e-05 + 4.049396940386240e-21i 2.200735779547360e-05 - 5.801816180125950e-21i 1.958498402017600e-05 + 1.484458348742240e-20i 1.719258564065160e-05 - 1.157190500364670e-20i 1.280389614211330e-05 + 7.361486718345000e-20i 8.730595135820959e-06 + 1.230644356263810e-20i 6.286185949706520e-06 - 5.042673277443530e-20i 6.999914698930080e-08 - 1.024508915006500e-20i 2.803439317569630e-08 + 1.230480320176860e-20i 4.297138319235120e-09 + 3.739086339682050e-21i 2.288026041745470e-09 + 1.735006489800580e-20i 3.505074672968440e-10 - 1.101591158203060e-21i 7.329736897389230e-11 - 4.650999929852550e-21i 2.078081700747650e-11 - 2.849663740488030e-22i 4.685106728960020e-12 - 2.295032000853010e-21i 2.990514033131900e-12 + 3.625050723818340e-21i 1.323993648036250e-12 - 4.302617783602930e-21i 6.072129157771810e-13 + 2.790630283876830e-22i 1.230865533648930e-13 + 8.265600042616479e-21i 1.723925207593810e-14 + 1.860191920864090e-21i 1.019896803549650e-14 + 3.461363594672200e-21i 1.368229097188400e-15 - 1.332215289890100e-21i -8.059189552450671e-21 + 8.233174086931050e-22i

@Cris LaPierre Thanks！

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