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How can I get Mathematica to find the index position of the first value in the list that is over 4 (6 in this case). I tried Position[L, L > 4] , but this gave ...

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Position[expr, pattern] gives a list of the positions at which objects matching pattern appear in expr. Position[expr, pattern, levelspec] finds only objects that appear on levels specified by levelspec. Position[expr, pattern, levelspec, n] gives the positions of the first n objects found. Position[pattern] represents an operator form of Position that can be applied to an expression.

7. This answer is not useful. Show activity on this post. In version 10 there is a new function FirstPosition: L = {2, 4, 6, 8, 10}; FirstPosition [ L, x_ /; x > 4] {3} The second argument of Position as welll as of FirstPosition is a pattern, so this would yield what you seemed to expect: Position [ L, x_ /; x > 4] { {3}, {4}, {5}}

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Wolfram Community forum discussion about FirstPosition[ls, SelectFirst[ls, # >= 1 &]]. Stay on top of important topics and build connections by joining Wolfram Community groups relevant to …

Aug 27, 2011 · Using Select will solve the problem, but it is a poor solution if you care about efficiency.Select goes over all the elements of the list, and therefore will take time which is linear in the length of the list.

@Daniel, Position[] can be made to return only the first position but I assume (based on timing results) it still checks the entire list.

27.08.2011 · I changed the Ceiling function to a Floor function to correctly handle recurring elements in the list. It is needed because if the threshold is between elements n and n+1 then BinarySearch returns n+1/2.The code I wrote works perfectly, and does indeed return the first (leftmost) element which is greater than the threshold (the request was not for a matching …

FirstPosition[expr, pattern] gives the position of the first element in expr that matches pattern, or Missing["NotFound"] if no such element is found. FirstPosition[expr, pattern, default] gives default if no element matching pattern is found. FirstPosition[expr, pattern, default, levelspec] finds only objects that appear on levels specified by levelspec.

Say I have a list x= {2,4,6,8,10} and I want to find out the positions of the elements that are greater than 7. Select [x, #>7&] gives the elements themselves, and Position [x,8] gives the position of the elements satisfying one of the possible criteria, but what I am looking for would be a mix of the two returning {4,5}.

Why is mathematica so slow when tables reach a certain lengthStop Canonical Ordering of Output ListEquivalent of numpy's newaxisPattern matching for ...

FirstPosition[l, #][[1]]} &[Min[l]] // AbsoluteTiming (* {6.08502, {4.91679*10^-8, 7830224}} *). Open Mathematica Notebook.

_?(# >= 1 &) I think Mathematica needs a LastPosition function as much as it needs FirstPosition.

How can I get Mathematica to find the index position of the first value in the list that is over 4 ... In version 10 there is a new function FirstPosition :

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Parts of Lists. Part lets you pick out an element of a list. [ [ ... ]] is an alternative notation. You can ask for a list of parts by giving a list of part numbers. ;; lets you ask for a span or sequence of parts. Let ’ s now talk about lists of lists, or arrays. Each sublist acts as a row in the array.

Wolfram Community forum discussion about FirstPosition[ls, SelectFirst[ls, # >= 1 &]]. Stay on top of important topics and build connections by joining Wolfram Community groups relevant to your interests.

mathematica 中Position函数 怎么强制运算匹配项

FirstPosition [ list, pattern, default, { 1 }, Heads -> False] finds positions only of objects that appear as complete elements of list. A positive level n consists of all parts of expr specified by n indices. A negative level - n consists of all parts of expr with depth n. Level 0 corresponds to the whole expression.

19.10.2011 · This is another simple 'matrix' question in Mathematica. I want to show how I did this, and ask if there is a better answer. I want to select all 'rows' from matrix based on value in the first column (or any column, I used first column here just as an example).

Position returns a list of positions in a form suitable for use in Extract, ReplacePart, and MapAt. The form is different from the one used in Part. Position looks only for matches to values in Association objects that appear in expr. It returns any part specifications within Association objects in the form Key [ k].

Ordering[list] gives the positions in list at which each successive element of Sort[list] appears. Ordering[list, n] gives the positions in list at which the first n elements of Sort[list] appear. Ordering[list, -n] gives the positions of the last n elements of Sort[list]. Ordering[list, n, p] gives positions in list of elements of Sort[list, p].

(* Content-type: application/vnd.wolfram.mathematica *). (*** Wolfram Notebook File ***). (* http://www.wolfram.com/nb *). (* CreatedBy='Mathematica 11.2' ...