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Results tagged with list-manipulation
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user 251
Questions on the manipulation of List objects in Mathematica, and the functions used for these manipulations.
7
votes
Changing sign of elements of a list on even positions
This is one way:
MapIndexed[{n, pos} |-> If[ EvenQ @ Last @ pos, -n, n], list, {2}]
- 8,727
6
votes
Insert a list within another without extra brackets
Using Sequence (for older versions of WL without Splice):
list1 = {{1, -1.1}, {2, -1}, {3, -0.9}, {4, 0}, {10, -0.4}};
list2 = {{2, -0.6}, {3, -0.6}};
Insert[list1, Inactive[Sequence] @@ list2, 3] // …
- 8,727
1
vote
Pairing headers with each subsequent entry in a flattened list
This is based on @Swish answer, but keeping everything string based:
With[{separatorQ = StringMatchQ["a-" ~~ DigitCharacter]},
Flatten[
SequenceCases[
oldList,
{
left : _Stri …
- 8,727
4
votes
Map-Thread-Through-Apply a list of functions onto a list of (lists of) values
Yet another solution:
Transpose[Activate[Thread[Inactive[Map][fns, Transpose[list]]]]]
- 8,727
4
votes
Creating a list with Thread
I think that the most natural way of doing this is by using MapIndexed. But if you want to use Range and Thread, this is one way:
{{11, 21, 31}, {12, 22, 32}, {13, 23, 33}} //
{Length /* Range, Iden …
- 8,727
4
votes
Span a function across several consecutive elements in a list
How about this way:
spanMap[f_, list_, {start_, end_}] := Replace[
MapAt[f, list,
List /@ Range[start, end]] /. {x___Integer,
seq : (PatternSequence[f[_] ..]), y___Integer} :> {x, {seq …
- 8,727
7
votes
Manipulating Elements in a Triple-Nested List
This command may be helpful to you:
MapAt[2 # &,
{{{44.5, 0.00185}, {45.2, 0.00186}, {45.5, 0.00186}},
{{48.6, 0.00186}, {49.2, 0.00209}, {49.9, 0.00109}}}, {All, All, 2}]
It produces this outpu …
- 8,727
2
votes
Selecting list elements depending if they contain sub-list elements
It is also possible by using rules:
cc /. {s_Symbol, pair_List} /; !MemberQ[Join[aa, bb], pair] -> Nothing
- 8,727
2
votes
Extract output from FindMaximum inside a function
Perhaps it is more intuitive if we use rules:
FindMaximum[{3 x, x < 1}, x] /. {result_, {x -> _}} -> result
- 8,727
2
votes
Duplicating entry values of a list to match varying number of sublist entries
How about:
Flatten[abc /. {x_Integer, {y : _List ...}} :> Thread[{x, Join@y}], 1]
(* {{{1, 1}, {1, 2}}, {{2, 3}, {2, 4}, {2, 5}}, {{3, 2}}} *)
- 8,727
1
vote
Pure function on pure function
This is one way:
Map[max |-> SelectFirst[t1, # > max &], t2]
and another way as three separate functional operations:
t2 //
Map[GreaterThan/*SelectFirst] //
OperatorApplied[Construct][t1] //
Th …
- 8,727
1
vote
How to show the whole table
This is one way:
{{7, 6}, {2, 4}} //
ReplaceAll[v_?VectorQ :> (v /. Min[v] -> Item[Min[v], Background -> Red])] //
Legended[Grid[#, Dividers -> All], SwatchLegend[{Red}, {"minimum"}]] &
- 8,727
4
votes
Transform sequence into ragged list
Lets process this using Fold. We will replace each number with a list consisting of the number, and its depth:
g[{level_, current_List}, element_Integer] := {level, Append[current, {element, level}]}
…
- 8,727
4
votes
How to remove extra brackets from a list?
Can also be done like this:
Query[All, Splice][list1]
- 8,727
3
votes
4
answers
137
views
Deleting or replacing inner elements depending on higher level elements
Consider a data structure like:
data = {{"experiment"->1, "tags"->{"type"->1}, "results"->{{"x", 2}, {"y", 5}, {"z", 5}}},
{"experiment"->2, "tags"->{"type"->2}, "results"->{{"x", 1}, {"y", 2 …
- 8,727