Terse Method to Swap Lowest for Highest?
$begingroup$
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
edited 26 mins ago
m_goldberg
87.7k872198
asked 1 hour ago
EdmundEdmund
26.6k330102
$endgroup$
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
edited 26 mins ago
m_goldberg
87.7k872198
asked 1 hour ago
EdmundEdmund
26.6k330102
$endgroup$
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
edited 26 mins ago
m_goldberg
87.7k872198
asked 1 hour ago
EdmundEdmund
26.6k330102
$endgroup$
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
list-manipulation performance-tuning sorting
edited 26 mins ago
m_goldberg
87.7k872198
asked 1 hour ago
EdmundEdmund
26.6k330102
edited 26 mins ago
m_goldberg
87.7k872198
asked 1 hour ago
EdmundEdmund
26.6k330102
edited 26 mins ago
m_goldberg
87.7k872198
edited 26 mins ago
m_goldberg
87.7k872198
edited 26 mins ago
m_goldberg
87.7k872198
87.7k872198
asked 1 hour ago
EdmundEdmund
26.6k330102
asked 1 hour ago
EdmundEdmund
26.6k330102
asked 1 hour ago
EdmundEdmund
26.6k330102
26.6k330102
add a comment |
add a comment |
1 Answer
1
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}
answered 50 mins ago
Carl WollCarl Woll
71.2k394185
$endgroup$
$begingroup$
That is so obvious I want to cry. Thanks (+1).
$endgroup$
– Edmund
45 mins ago
add a comment |
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1 Answer
1
active
oldest
votes
1 Answer
1
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}
answered 50 mins ago
Carl WollCarl Woll
71.2k394185
$endgroup$
$begingroup$
That is so obvious I want to cry. Thanks (+1).
$endgroup$
– Edmund
45 mins ago
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}
answered 50 mins ago
Carl WollCarl Woll
71.2k394185
$endgroup$
$begingroup$
That is so obvious I want to cry. Thanks (+1).
$endgroup$
– Edmund
45 mins ago
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}
answered 50 mins ago
Carl WollCarl Woll
71.2k394185
$endgroup$
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 50 mins ago
Carl WollCarl Woll
71.2k394185
answered 50 mins ago
Carl WollCarl Woll
71.2k394185
answered 50 mins ago
Carl WollCarl Woll
71.2k394185
answered 50 mins ago
Carl WollCarl Woll
71.2k394185
71.2k394185
$begingroup$
That is so obvious I want to cry. Thanks (+1).
$endgroup$
– Edmund
45 mins ago
add a comment |
$begingroup$
That is so obvious I want to cry. Thanks (+1).
$endgroup$
– Edmund
45 mins ago
$begingroup$
That is so obvious I want to cry. Thanks (+1).
$endgroup$
– Edmund
45 mins ago
$begingroup$
That is so obvious I want to cry. Thanks (+1).
$endgroup$
– Edmund
45 mins ago
add a comment |
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