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Terse Method to Swap Lowest for Highest?
Efficient method for Inserting arrays into arraysSwap elements in list without copyBetter method to swap the values of two 2-D arraysHow to get this list with a terse methodBuilt-in (or Terse) Method to Combine and Transpose DatasetsAre there more readable and terse method can get this listefficiently method for generating a sequenceSimple method to sort versionsFunction for SortBySwap Elements of a continuous List, possible?
$begingroup$
I have built a solution to swap the lowest values with the highest values in a list.
With
SeedRandom[987]
test = RandomSample@*Join @@ Range @@@ 6, 10, 56, 60, 1, 5, -5, -1
-1, 2, 7, 8, 60, 57, 58, 10, 9, 4, -5, -3, 3, 59, 1, 5, -4, 6, -2, 56
Then
swapPositions =
PermutationReplace[
Ordering@Ordering@test,
With[len = Length@test,
Cycles@
Transpose@Range @@ 1, Floor[len/2], Reverse@*Range @@ Ceiling[len/2] + 1, len
]
];
Sort[test][[swapPositions]]
56, 9, 4, 3, -5, -2, -3, 1, 2, 7, 60, 58, 8, -4, 10, 6, 59, 5, 57, -1
The largest half of the numbers have had their positions swapped with lowest half of the numbers.
However, it feels too verbose and I think Sort
might be expensive in this case. Is there a built-in function or more terse method to achieve this. Of course with no loss in speed. The actual case is for list of length 100000 and more.
list-manipulation performance-tuning sorting permutation
$endgroup$
add a comment |
$begingroup$
I have built a solution to swap the lowest values with the highest values in a list.
With
SeedRandom[987]
test = RandomSample@*Join @@ Range @@@ 6, 10, 56, 60, 1, 5, -5, -1
-1, 2, 7, 8, 60, 57, 58, 10, 9, 4, -5, -3, 3, 59, 1, 5, -4, 6, -2, 56
Then
swapPositions =
PermutationReplace[
Ordering@Ordering@test,
With[len = Length@test,
Cycles@
Transpose@Range @@ 1, Floor[len/2], Reverse@*Range @@ Ceiling[len/2] + 1, len
]
];
Sort[test][[swapPositions]]
56, 9, 4, 3, -5, -2, -3, 1, 2, 7, 60, 58, 8, -4, 10, 6, 59, 5, 57, -1
The largest half of the numbers have had their positions swapped with lowest half of the numbers.
However, it feels too verbose and I think Sort
might be expensive in this case. Is there a built-in function or more terse method to achieve this. Of course with no loss in speed. The actual case is for list of length 100000 and more.
list-manipulation performance-tuning sorting permutation
$endgroup$
add a comment |
$begingroup$
I have built a solution to swap the lowest values with the highest values in a list.
With
SeedRandom[987]
test = RandomSample@*Join @@ Range @@@ 6, 10, 56, 60, 1, 5, -5, -1
-1, 2, 7, 8, 60, 57, 58, 10, 9, 4, -5, -3, 3, 59, 1, 5, -4, 6, -2, 56
Then
swapPositions =
PermutationReplace[
Ordering@Ordering@test,
With[len = Length@test,
Cycles@
Transpose@Range @@ 1, Floor[len/2], Reverse@*Range @@ Ceiling[len/2] + 1, len
]
];
Sort[test][[swapPositions]]
56, 9, 4, 3, -5, -2, -3, 1, 2, 7, 60, 58, 8, -4, 10, 6, 59, 5, 57, -1
The largest half of the numbers have had their positions swapped with lowest half of the numbers.
However, it feels too verbose and I think Sort
might be expensive in this case. Is there a built-in function or more terse method to achieve this. Of course with no loss in speed. The actual case is for list of length 100000 and more.
list-manipulation performance-tuning sorting permutation
$endgroup$
I have built a solution to swap the lowest values with the highest values in a list.
With
SeedRandom[987]
test = RandomSample@*Join @@ Range @@@ 6, 10, 56, 60, 1, 5, -5, -1
-1, 2, 7, 8, 60, 57, 58, 10, 9, 4, -5, -3, 3, 59, 1, 5, -4, 6, -2, 56
Then
swapPositions =
PermutationReplace[
Ordering@Ordering@test,
With[len = Length@test,
Cycles@
Transpose@Range @@ 1, Floor[len/2], Reverse@*Range @@ Ceiling[len/2] + 1, len
]
];
Sort[test][[swapPositions]]
56, 9, 4, 3, -5, -2, -3, 1, 2, 7, 60, 58, 8, -4, 10, 6, 59, 5, 57, -1
The largest half of the numbers have had their positions swapped with lowest half of the numbers.
However, it feels too verbose and I think Sort
might be expensive in this case. Is there a built-in function or more terse method to achieve this. Of course with no loss in speed. The actual case is for list of length 100000 and more.
list-manipulation performance-tuning sorting permutation
list-manipulation performance-tuning sorting permutation
edited Mar 23 at 2:15
J. M. is away♦
99k10311470
99k10311470
asked Mar 22 at 20:57
EdmundEdmund
26.9k330103
26.9k330103
add a comment |
add a comment |
2 Answers
2
active
oldest
votes
$begingroup$
How about:
Module[tmp = test,
With[ord=Ordering[tmp],
tmp[[ord]] = Reverse @ tmp[[ord]]];
tmp
]
56, 9, 4, 3, -5, -2, -3, 1, 2, 7, 60, 58, 8, -4, 10, 6, 59, 5, 57, -1
$endgroup$
1
$begingroup$
That is so obvious I want to cry. Thanks (+1).
$endgroup$
– Edmund
Mar 22 at 21:15
add a comment |
$begingroup$
This is equivalent to Carl's procedure, except that it uses one less scratch list:
With[ord = Ordering[test],
test[[PermutationProduct[Reverse[ord], InversePermutation[ord]]]]]
56, 9, 4, 3, -5, -2, -3, 1, 2, 7, 60, 58, 8, -4, 10, 6, 59, 5, 57, -1
Recall that list[[perm]] = list
is equivalent to list = list[[InversePermutation[perm]]]
, where perm
is a permutation list. (The situation is equivalent to list.pmat
being the same as Transpose[pmat].list
if pmat
is a permutation matrix.) You can then use PermutationProduct[]
to compose successive permutations.
(This was supposed to be a comment, but it got too long.)
$endgroup$
$begingroup$
This solution doesn't copy the list so may be faster than Carl's. (+1).
$endgroup$
– Edmund
Mar 23 at 3:38
$begingroup$
FWIW, I consistently get 56, -2, 6, -4, 5, 1, 59, 3, -3, -5, 4, 9, 10, 58, 57, 60, 8, 7, 2, -1 from this.
$endgroup$
– Christopher Lamb
Mar 23 at 16:01
$begingroup$
@Rabbit, what version number of Mathematica is giving that result?
$endgroup$
– J. M. is away♦
Mar 23 at 16:10
$begingroup$
11.3.0.0 (5944644, 2018030701) Win 10. I did a trace, which might have had the needed info but I didn't catch it. Started w/ fresh kernel, & repeated, w/ same result. Baffled.
$endgroup$
– Christopher Lamb
Mar 23 at 16:16
1
$begingroup$
At least on my machine, the questioner's original (very verbose) proposed solution is faster than any other proposal. In order of presentation: 0.0000114366 v. 0.0000357762 v. 0.0000164219 (AbsoluteTiming in seconds).
$endgroup$
– CElliott
Apr 3 at 14:10
|
show 3 more comments
Your Answer
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
$begingroup$
How about:
Module[tmp = test,
With[ord=Ordering[tmp],
tmp[[ord]] = Reverse @ tmp[[ord]]];
tmp
]
56, 9, 4, 3, -5, -2, -3, 1, 2, 7, 60, 58, 8, -4, 10, 6, 59, 5, 57, -1
$endgroup$
1
$begingroup$
That is so obvious I want to cry. Thanks (+1).
$endgroup$
– Edmund
Mar 22 at 21:15
add a comment |
$begingroup$
How about:
Module[tmp = test,
With[ord=Ordering[tmp],
tmp[[ord]] = Reverse @ tmp[[ord]]];
tmp
]
56, 9, 4, 3, -5, -2, -3, 1, 2, 7, 60, 58, 8, -4, 10, 6, 59, 5, 57, -1
$endgroup$
1
$begingroup$
That is so obvious I want to cry. Thanks (+1).
$endgroup$
– Edmund
Mar 22 at 21:15
add a comment |
$begingroup$
How about:
Module[tmp = test,
With[ord=Ordering[tmp],
tmp[[ord]] = Reverse @ tmp[[ord]]];
tmp
]
56, 9, 4, 3, -5, -2, -3, 1, 2, 7, 60, 58, 8, -4, 10, 6, 59, 5, 57, -1
$endgroup$
How about:
Module[tmp = test,
With[ord=Ordering[tmp],
tmp[[ord]] = Reverse @ tmp[[ord]]];
tmp
]
56, 9, 4, 3, -5, -2, -3, 1, 2, 7, 60, 58, 8, -4, 10, 6, 59, 5, 57, -1
answered Mar 22 at 21:11
Carl WollCarl Woll
76.8k3101201
76.8k3101201
1
$begingroup$
That is so obvious I want to cry. Thanks (+1).
$endgroup$
– Edmund
Mar 22 at 21:15
add a comment |
1
$begingroup$
That is so obvious I want to cry. Thanks (+1).
$endgroup$
– Edmund
Mar 22 at 21:15
1
1
$begingroup$
That is so obvious I want to cry. Thanks (+1).
$endgroup$
– Edmund
Mar 22 at 21:15
$begingroup$
That is so obvious I want to cry. Thanks (+1).
$endgroup$
– Edmund
Mar 22 at 21:15
add a comment |
$begingroup$
This is equivalent to Carl's procedure, except that it uses one less scratch list:
With[ord = Ordering[test],
test[[PermutationProduct[Reverse[ord], InversePermutation[ord]]]]]
56, 9, 4, 3, -5, -2, -3, 1, 2, 7, 60, 58, 8, -4, 10, 6, 59, 5, 57, -1
Recall that list[[perm]] = list
is equivalent to list = list[[InversePermutation[perm]]]
, where perm
is a permutation list. (The situation is equivalent to list.pmat
being the same as Transpose[pmat].list
if pmat
is a permutation matrix.) You can then use PermutationProduct[]
to compose successive permutations.
(This was supposed to be a comment, but it got too long.)
$endgroup$
$begingroup$
This solution doesn't copy the list so may be faster than Carl's. (+1).
$endgroup$
– Edmund
Mar 23 at 3:38
$begingroup$
FWIW, I consistently get 56, -2, 6, -4, 5, 1, 59, 3, -3, -5, 4, 9, 10, 58, 57, 60, 8, 7, 2, -1 from this.
$endgroup$
– Christopher Lamb
Mar 23 at 16:01
$begingroup$
@Rabbit, what version number of Mathematica is giving that result?
$endgroup$
– J. M. is away♦
Mar 23 at 16:10
$begingroup$
11.3.0.0 (5944644, 2018030701) Win 10. I did a trace, which might have had the needed info but I didn't catch it. Started w/ fresh kernel, & repeated, w/ same result. Baffled.
$endgroup$
– Christopher Lamb
Mar 23 at 16:16
1
$begingroup$
At least on my machine, the questioner's original (very verbose) proposed solution is faster than any other proposal. In order of presentation: 0.0000114366 v. 0.0000357762 v. 0.0000164219 (AbsoluteTiming in seconds).
$endgroup$
– CElliott
Apr 3 at 14:10
|
show 3 more comments
$begingroup$
This is equivalent to Carl's procedure, except that it uses one less scratch list:
With[ord = Ordering[test],
test[[PermutationProduct[Reverse[ord], InversePermutation[ord]]]]]
56, 9, 4, 3, -5, -2, -3, 1, 2, 7, 60, 58, 8, -4, 10, 6, 59, 5, 57, -1
Recall that list[[perm]] = list
is equivalent to list = list[[InversePermutation[perm]]]
, where perm
is a permutation list. (The situation is equivalent to list.pmat
being the same as Transpose[pmat].list
if pmat
is a permutation matrix.) You can then use PermutationProduct[]
to compose successive permutations.
(This was supposed to be a comment, but it got too long.)
$endgroup$
$begingroup$
This solution doesn't copy the list so may be faster than Carl's. (+1).
$endgroup$
– Edmund
Mar 23 at 3:38
$begingroup$
FWIW, I consistently get 56, -2, 6, -4, 5, 1, 59, 3, -3, -5, 4, 9, 10, 58, 57, 60, 8, 7, 2, -1 from this.
$endgroup$
– Christopher Lamb
Mar 23 at 16:01
$begingroup$
@Rabbit, what version number of Mathematica is giving that result?
$endgroup$
– J. M. is away♦
Mar 23 at 16:10
$begingroup$
11.3.0.0 (5944644, 2018030701) Win 10. I did a trace, which might have had the needed info but I didn't catch it. Started w/ fresh kernel, & repeated, w/ same result. Baffled.
$endgroup$
– Christopher Lamb
Mar 23 at 16:16
1
$begingroup$
At least on my machine, the questioner's original (very verbose) proposed solution is faster than any other proposal. In order of presentation: 0.0000114366 v. 0.0000357762 v. 0.0000164219 (AbsoluteTiming in seconds).
$endgroup$
– CElliott
Apr 3 at 14:10
|
show 3 more comments
$begingroup$
This is equivalent to Carl's procedure, except that it uses one less scratch list:
With[ord = Ordering[test],
test[[PermutationProduct[Reverse[ord], InversePermutation[ord]]]]]
56, 9, 4, 3, -5, -2, -3, 1, 2, 7, 60, 58, 8, -4, 10, 6, 59, 5, 57, -1
Recall that list[[perm]] = list
is equivalent to list = list[[InversePermutation[perm]]]
, where perm
is a permutation list. (The situation is equivalent to list.pmat
being the same as Transpose[pmat].list
if pmat
is a permutation matrix.) You can then use PermutationProduct[]
to compose successive permutations.
(This was supposed to be a comment, but it got too long.)
$endgroup$
This is equivalent to Carl's procedure, except that it uses one less scratch list:
With[ord = Ordering[test],
test[[PermutationProduct[Reverse[ord], InversePermutation[ord]]]]]
56, 9, 4, 3, -5, -2, -3, 1, 2, 7, 60, 58, 8, -4, 10, 6, 59, 5, 57, -1
Recall that list[[perm]] = list
is equivalent to list = list[[InversePermutation[perm]]]
, where perm
is a permutation list. (The situation is equivalent to list.pmat
being the same as Transpose[pmat].list
if pmat
is a permutation matrix.) You can then use PermutationProduct[]
to compose successive permutations.
(This was supposed to be a comment, but it got too long.)
edited Mar 23 at 2:27
answered Mar 23 at 2:14
J. M. is away♦J. M. is away
99k10311470
99k10311470
$begingroup$
This solution doesn't copy the list so may be faster than Carl's. (+1).
$endgroup$
– Edmund
Mar 23 at 3:38
$begingroup$
FWIW, I consistently get 56, -2, 6, -4, 5, 1, 59, 3, -3, -5, 4, 9, 10, 58, 57, 60, 8, 7, 2, -1 from this.
$endgroup$
– Christopher Lamb
Mar 23 at 16:01
$begingroup$
@Rabbit, what version number of Mathematica is giving that result?
$endgroup$
– J. M. is away♦
Mar 23 at 16:10
$begingroup$
11.3.0.0 (5944644, 2018030701) Win 10. I did a trace, which might have had the needed info but I didn't catch it. Started w/ fresh kernel, & repeated, w/ same result. Baffled.
$endgroup$
– Christopher Lamb
Mar 23 at 16:16
1
$begingroup$
At least on my machine, the questioner's original (very verbose) proposed solution is faster than any other proposal. In order of presentation: 0.0000114366 v. 0.0000357762 v. 0.0000164219 (AbsoluteTiming in seconds).
$endgroup$
– CElliott
Apr 3 at 14:10
|
show 3 more comments
$begingroup$
This solution doesn't copy the list so may be faster than Carl's. (+1).
$endgroup$
– Edmund
Mar 23 at 3:38
$begingroup$
FWIW, I consistently get 56, -2, 6, -4, 5, 1, 59, 3, -3, -5, 4, 9, 10, 58, 57, 60, 8, 7, 2, -1 from this.
$endgroup$
– Christopher Lamb
Mar 23 at 16:01
$begingroup$
@Rabbit, what version number of Mathematica is giving that result?
$endgroup$
– J. M. is away♦
Mar 23 at 16:10
$begingroup$
11.3.0.0 (5944644, 2018030701) Win 10. I did a trace, which might have had the needed info but I didn't catch it. Started w/ fresh kernel, & repeated, w/ same result. Baffled.
$endgroup$
– Christopher Lamb
Mar 23 at 16:16
1
$begingroup$
At least on my machine, the questioner's original (very verbose) proposed solution is faster than any other proposal. In order of presentation: 0.0000114366 v. 0.0000357762 v. 0.0000164219 (AbsoluteTiming in seconds).
$endgroup$
– CElliott
Apr 3 at 14:10
$begingroup$
This solution doesn't copy the list so may be faster than Carl's. (+1).
$endgroup$
– Edmund
Mar 23 at 3:38
$begingroup$
This solution doesn't copy the list so may be faster than Carl's. (+1).
$endgroup$
– Edmund
Mar 23 at 3:38
$begingroup$
FWIW, I consistently get 56, -2, 6, -4, 5, 1, 59, 3, -3, -5, 4, 9, 10, 58, 57, 60, 8, 7, 2, -1 from this.
$endgroup$
– Christopher Lamb
Mar 23 at 16:01
$begingroup$
FWIW, I consistently get 56, -2, 6, -4, 5, 1, 59, 3, -3, -5, 4, 9, 10, 58, 57, 60, 8, 7, 2, -1 from this.
$endgroup$
– Christopher Lamb
Mar 23 at 16:01
$begingroup$
@Rabbit, what version number of Mathematica is giving that result?
$endgroup$
– J. M. is away♦
Mar 23 at 16:10
$begingroup$
@Rabbit, what version number of Mathematica is giving that result?
$endgroup$
– J. M. is away♦
Mar 23 at 16:10
$begingroup$
11.3.0.0 (5944644, 2018030701) Win 10. I did a trace, which might have had the needed info but I didn't catch it. Started w/ fresh kernel, & repeated, w/ same result. Baffled.
$endgroup$
– Christopher Lamb
Mar 23 at 16:16
$begingroup$
11.3.0.0 (5944644, 2018030701) Win 10. I did a trace, which might have had the needed info but I didn't catch it. Started w/ fresh kernel, & repeated, w/ same result. Baffled.
$endgroup$
– Christopher Lamb
Mar 23 at 16:16
1
1
$begingroup$
At least on my machine, the questioner's original (very verbose) proposed solution is faster than any other proposal. In order of presentation: 0.0000114366 v. 0.0000357762 v. 0.0000164219 (AbsoluteTiming in seconds).
$endgroup$
– CElliott
Apr 3 at 14:10
$begingroup$
At least on my machine, the questioner's original (very verbose) proposed solution is faster than any other proposal. In order of presentation: 0.0000114366 v. 0.0000357762 v. 0.0000164219 (AbsoluteTiming in seconds).
$endgroup$
– CElliott
Apr 3 at 14:10
|
show 3 more comments
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