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Delete elements less than the last largest element

Deleting multiple elements from a listChanging the precision of data in a list of matricesJoin nested lists based on first and last elements within each listUsing Select function to select elements based on last element of nested listDelete only when there are two (or more) 1smaking two columns from 1D-horizontal dataDelete some elements based on the keysHow to set a particular element of a list to a number?delete an element list recursivelyElegant way of partitioning in two starting from the second element?

.everyoneloves__top-leaderboard:empty,.everyoneloves__mid-leaderboard:empty,.everyoneloves__bot-mid-leaderboard:empty{ margin-bottom:0;
}

3

$begingroup$

Here is my list. The first column contains its index and second column has data.

list={{1, 170.93}, {2, 170.4}, {3, 174.08}, {4, 160.65}, {5, 166.44}, {6, 

      169.75}, {7, 175.86}, {8, 177.6}, {9, 180.27}, {10, 182.82}, {11, 

      182.02}, {12, 186.65}, {13, 184.53}, {14, 186.17}, {15, 

     177.29}, {16, 172.06}, {17, 175.58}, {18, 168.09}, {19, 

     172.33}, {20, 165.1}, {21, 154.88}, {22, 161.28}, {23, 165.25}, {24,

     165.15}, {25, 171.03}, {26, 174.55}, {27, 182.57}, {28, 

     191.02}, {29, 191.11}, {30, 184.93}, {31, 188.85}, {32, 191.44}};

I want to delete all numbers that are smaller than the last largest element. For example, I want to delete 4th, 5th and 6th elements because they are smaller than the last largest element (3rd). Similarly, I want to delete elements from 13th to 27th elements because they are smaller than the last largest element (12th). 30th and 31st elements should be deleted because they are smaller than prior largest element (29th). Final results should contain increasing numbers. Here is the tabular representation of the data:

I did my best to explain my problem. Please write in the comment if it is not clear. I have a big data and I need to manipulate it as explained here. Any help would be greatly appreciated. Thanks

list-manipulation programming

share|improve this question

asked 8 hours ago

DestinationLess_TravellerDestinationLess_Traveller

12955 bronze badges

$endgroup$

• 
  
  
  

  
  4
  

  
  
  
  
  
  

  
  $begingroup$
  DeleteDuplicatesBy[ Transpose[{list[[All, 1]], FoldList[Max, list[[All, 2]]]}], Last] should do what you're after.
  $endgroup$
  – ciao
  8 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  Should you also be deleting the second element since it is smaller than the first? I will note that the solution from @ciao does remove the second element.
  $endgroup$
  – Mark R
  7 hours ago
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  @ Mark R, yes you are right. I missed it. Thanks
  $endgroup$
  – DestinationLess_Traveller
  7 hours ago
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  $begingroup$
  DeleteDuplicates[list, #1[[2]] > #2[[2]] &]
  $endgroup$
  – Bob Hanlon
  7 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  @ Bob, thanks for your simple answer. I really appreciate it.
  $endgroup$
  – DestinationLess_Traveller
  2 hours ago
  

  
  
  
  

add a comment | 

3

$begingroup$

Here is my list. The first column contains its index and second column has data.

list={{1, 170.93}, {2, 170.4}, {3, 174.08}, {4, 160.65}, {5, 166.44}, {6, 

      169.75}, {7, 175.86}, {8, 177.6}, {9, 180.27}, {10, 182.82}, {11, 

      182.02}, {12, 186.65}, {13, 184.53}, {14, 186.17}, {15, 

     177.29}, {16, 172.06}, {17, 175.58}, {18, 168.09}, {19, 

     172.33}, {20, 165.1}, {21, 154.88}, {22, 161.28}, {23, 165.25}, {24,

     165.15}, {25, 171.03}, {26, 174.55}, {27, 182.57}, {28, 

     191.02}, {29, 191.11}, {30, 184.93}, {31, 188.85}, {32, 191.44}};

I want to delete all numbers that are smaller than the last largest element. For example, I want to delete 4th, 5th and 6th elements because they are smaller than the last largest element (3rd). Similarly, I want to delete elements from 13th to 27th elements because they are smaller than the last largest element (12th). 30th and 31st elements should be deleted because they are smaller than prior largest element (29th). Final results should contain increasing numbers. Here is the tabular representation of the data:

I did my best to explain my problem. Please write in the comment if it is not clear. I have a big data and I need to manipulate it as explained here. Any help would be greatly appreciated. Thanks

list-manipulation programming

share|improve this question

asked 8 hours ago

DestinationLess_TravellerDestinationLess_Traveller

12955 bronze badges

$endgroup$

• 
  
  
  

  
  4
  

  
  
  
  
  
  

  
  $begingroup$
  DeleteDuplicatesBy[ Transpose[{list[[All, 1]], FoldList[Max, list[[All, 2]]]}], Last] should do what you're after.
  $endgroup$
  – ciao
  8 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  Should you also be deleting the second element since it is smaller than the first? I will note that the solution from @ciao does remove the second element.
  $endgroup$
  – Mark R
  7 hours ago
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  @ Mark R, yes you are right. I missed it. Thanks
  $endgroup$
  – DestinationLess_Traveller
  7 hours ago
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  $begingroup$
  DeleteDuplicates[list, #1[[2]] > #2[[2]] &]
  $endgroup$
  – Bob Hanlon
  7 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  @ Bob, thanks for your simple answer. I really appreciate it.
  $endgroup$
  – DestinationLess_Traveller
  2 hours ago
  

  
  
  
  

add a comment | 

$begingroup$

Here is my list. The first column contains its index and second column has data.

list={{1, 170.93}, {2, 170.4}, {3, 174.08}, {4, 160.65}, {5, 166.44}, {6, 

      169.75}, {7, 175.86}, {8, 177.6}, {9, 180.27}, {10, 182.82}, {11, 

      182.02}, {12, 186.65}, {13, 184.53}, {14, 186.17}, {15, 

     177.29}, {16, 172.06}, {17, 175.58}, {18, 168.09}, {19, 

     172.33}, {20, 165.1}, {21, 154.88}, {22, 161.28}, {23, 165.25}, {24,

     165.15}, {25, 171.03}, {26, 174.55}, {27, 182.57}, {28, 

     191.02}, {29, 191.11}, {30, 184.93}, {31, 188.85}, {32, 191.44}};

I want to delete all numbers that are smaller than the last largest element. For example, I want to delete 4th, 5th and 6th elements because they are smaller than the last largest element (3rd). Similarly, I want to delete elements from 13th to 27th elements because they are smaller than the last largest element (12th). 30th and 31st elements should be deleted because they are smaller than prior largest element (29th). Final results should contain increasing numbers. Here is the tabular representation of the data:

I did my best to explain my problem. Please write in the comment if it is not clear. I have a big data and I need to manipulate it as explained here. Any help would be greatly appreciated. Thanks

list-manipulation programming

share|improve this question

asked 8 hours ago

DestinationLess_TravellerDestinationLess_Traveller

12955 bronze badges

$endgroup$

list={{1, 170.93}, {2, 170.4}, {3, 174.08}, {4, 160.65}, {5, 166.44}, {6, 

      169.75}, {7, 175.86}, {8, 177.6}, {9, 180.27}, {10, 182.82}, {11, 

      182.02}, {12, 186.65}, {13, 184.53}, {14, 186.17}, {15, 

     177.29}, {16, 172.06}, {17, 175.58}, {18, 168.09}, {19, 

     172.33}, {20, 165.1}, {21, 154.88}, {22, 161.28}, {23, 165.25}, {24,

     165.15}, {25, 171.03}, {26, 174.55}, {27, 182.57}, {28, 

     191.02}, {29, 191.11}, {30, 184.93}, {31, 188.85}, {32, 191.44}};

share|improve this question

asked 8 hours ago

DestinationLess_TravellerDestinationLess_Traveller

12955 bronze badges

share|improve this question

asked 8 hours ago

DestinationLess_TravellerDestinationLess_Traveller

12955 bronze badges

asked 8 hours ago

DestinationLess_TravellerDestinationLess_Traveller

12955 bronze badges

asked 8 hours ago

DestinationLess_TravellerDestinationLess_Traveller

12955 bronze badges

1 Answer
1

active

oldest

votes

4

$begingroup$

TakeList[list, Length /@ Split[FoldList[Max, list[[All, 2]]]]][[All, 1]]

{{1, 170.93}, {3, 174.08}, {7, 175.86}, {8, 177.6}, {9, 180.27}, {10,
182.82}, {12, 186.65}, {28, 191.02}, {29, 191.11}, {32, 191.44}}

Also

max = list[[1, -1]];

Split[list, Or[Last[#2] < max, max = Last[#2]] &][[All, 1]]

same result

DeleteDuplicates[Join @@ FoldList[MaximalBy[Last] @* Append, {First @ list}, 

   Rest @ list]]

same result

The first method is much faster.

share|improve this answer

edited 7 hours ago

answered 7 hours ago

kglrkglr

203k1010 gold badges232232 silver badges463463 bronze badges

$endgroup$

• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  Thank you kglr.
  $endgroup$
  – DestinationLess_Traveller
  6 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  @DestinationLess_Traveller, thank you for the accept.
  $endgroup$
  – kglr
  6 hours ago
  

  
  
  
  

add a comment | 

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4

$begingroup$

TakeList[list, Length /@ Split[FoldList[Max, list[[All, 2]]]]][[All, 1]]

{{1, 170.93}, {3, 174.08}, {7, 175.86}, {8, 177.6}, {9, 180.27}, {10,
182.82}, {12, 186.65}, {28, 191.02}, {29, 191.11}, {32, 191.44}}

Also

max = list[[1, -1]];

Split[list, Or[Last[#2] < max, max = Last[#2]] &][[All, 1]]

same result

DeleteDuplicates[Join @@ FoldList[MaximalBy[Last] @* Append, {First @ list}, 

   Rest @ list]]

same result

The first method is much faster.

share|improve this answer

edited 7 hours ago

answered 7 hours ago

kglrkglr

203k1010 gold badges232232 silver badges463463 bronze badges

$endgroup$

• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  Thank you kglr.
  $endgroup$
  – DestinationLess_Traveller
  6 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  @DestinationLess_Traveller, thank you for the accept.
  $endgroup$
  – kglr
  6 hours ago
  

  
  
  
  

add a comment | 

4

$begingroup$

TakeList[list, Length /@ Split[FoldList[Max, list[[All, 2]]]]][[All, 1]]

{{1, 170.93}, {3, 174.08}, {7, 175.86}, {8, 177.6}, {9, 180.27}, {10,
182.82}, {12, 186.65}, {28, 191.02}, {29, 191.11}, {32, 191.44}}

Also

max = list[[1, -1]];

Split[list, Or[Last[#2] < max, max = Last[#2]] &][[All, 1]]

same result

DeleteDuplicates[Join @@ FoldList[MaximalBy[Last] @* Append, {First @ list}, 

   Rest @ list]]

same result

The first method is much faster.

share|improve this answer

edited 7 hours ago

answered 7 hours ago

kglrkglr

203k1010 gold badges232232 silver badges463463 bronze badges

$endgroup$

• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  Thank you kglr.
  $endgroup$
  – DestinationLess_Traveller
  6 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  @DestinationLess_Traveller, thank you for the accept.
  $endgroup$
  – kglr
  6 hours ago
  

  
  
  
  

add a comment | 

$begingroup$

TakeList[list, Length /@ Split[FoldList[Max, list[[All, 2]]]]][[All, 1]]

{{1, 170.93}, {3, 174.08}, {7, 175.86}, {8, 177.6}, {9, 180.27}, {10,
182.82}, {12, 186.65}, {28, 191.02}, {29, 191.11}, {32, 191.44}}

Also

max = list[[1, -1]];

Split[list, Or[Last[#2] < max, max = Last[#2]] &][[All, 1]]

same result

DeleteDuplicates[Join @@ FoldList[MaximalBy[Last] @* Append, {First @ list}, 

   Rest @ list]]

same result

The first method is much faster.

share|improve this answer

edited 7 hours ago

answered 7 hours ago

kglrkglr

203k1010 gold badges232232 silver badges463463 bronze badges

$endgroup$

TakeList[list, Length /@ Split[FoldList[Max, list[[All, 2]]]]][[All, 1]]

max = list[[1, -1]];

Split[list, Or[Last[#2] < max, max = Last[#2]] &][[All, 1]]

DeleteDuplicates[Join @@ FoldList[MaximalBy[Last] @* Append, {First @ list}, 

   Rest @ list]]

share|improve this answer

edited 7 hours ago

answered 7 hours ago

kglrkglr

203k1010 gold badges232232 silver badges463463 bronze badges

answered 7 hours ago

kglrkglr

203k1010 gold badges232232 silver badges463463 bronze badges

answered 7 hours ago

kglrkglr

203k1010 gold badges232232 silver badges463463 bronze badges