Questions on the manipulation of List objects in Mathematica, and the functions used for these manipulations.

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4
votes
3answers
54 views

Turning a set of random walk data 45 degrees

I have a set of data that is just a "random" (generated by me, not by computer) sequence of length 2000 of 1's and (-1)'s. I used it to plot a 1-D random walk where +1 is step up, (-1) is step down, ...
0
votes
4answers
23 views

How do I write a condition for Position that uses both the current and previous element?

For example, given {57, 3, 40, 94, 9, 84, 81, 93, 76, 5, 7, 76, 38, 9, 23, 95, 49, 0, 30, 3} I'd like to get all the indices at which the elements cross from ...
5
votes
2answers
111 views

How can I generate a $2n$-point moving maximum of a list as efficiently as MaxFilter?

This is based on the prior question, Moving maximum function?, where @rasher provided two winning solutions (i.e. clearly the most efficient): MaxFilter[list, 1] ...
0
votes
4answers
64 views

Find all disjoint subsets of equal length

Suppose that $A$ is a list with $n$ elements where $n$ is even. I want to write a function that returns all pairs $(A_1,A_2)$ where the sets $A_1$ and $A_2$ each have length $\frac{n}{2}$, $A_1 \cap ...
0
votes
3answers
51 views

How to iterate through a list of rules?

Let's consider I have a list of rules: {Aa -> 1/2, Av -> 2/5, Bx -> 3/7, Ce -> 4/9, ...} I want to find all keys that contain the letter "A" and ...
17
votes
7answers
463 views

Faster position list construction from a “take instructions” list

Take some list, e.g., {1,2,3,4,5}, and a "take instructions" list, say {1,1,2,1,1}. The latter is read as "take the first ...
4
votes
2answers
86 views

How can I insert an element every $n$th position in a list?

How can I insert an element every $n$ positions in a list? For example, inserting a zero as every 4th element to turn {1, 2, 3, 4, 5, 6, 7} into ...
5
votes
2answers
280 views

Can someone explain this code for joining two lists by the first element of each sublist?

Background (which may be skipped, unless context is needed) I've recently begun learning Mathematica (and only up to chapter 3 of Wellin), but wanted to write some code to get a better feel for ...
1
vote
3answers
52 views

Selective data append to nested list

I have a list of database id and stock indicies which I use to withdraw the related price data. lis = {{4470, "^AEX"}, {4471, "^AFLI"}, {4472, "^AORD"}} I use ...
2
votes
2answers
78 views

Dynamic arrays and lists with compile (Append, Linked lists etc.)

I have a code that I need to compile. The code contains a loop in which I need to gather data into a list. The question is how to best gather data so that the code works inside Compile. The following ...
0
votes
0answers
22 views

Returning multiple results from compiled functions in M10 [duplicate]

I have found a similar question from 2012 here. It has been 3 years now and we have version 10. Have there been any attempt to solve this problem either by Wolfram or by the community - how to return ...
8
votes
1answer
80 views

Unexpected slowness checking for empty list?

I thought I had a firm understanding of the differences between Equal and SameQ, but this has me puzzled: ...
1
vote
1answer
38 views

Change date format in nested lists

I have a list of index symbols and data as follows: ...
2
votes
1answer
45 views

Evaluate recursive funtion as a whole before computing a recursive step

I'll try to make a basic example of my problem with $n$ being an array of elements, ex. $\{1,2,2,3,3,3\}$: If i have a sum which needs a computed value i would like to compute it beforehand and store ...
0
votes
2answers
71 views

Sorting non-numerical lists [duplicate]

The Sort function will by default sort from lowest to highest. In[1]:= Sort[{3, 1, 4}] Out[1]= {1, 3, 4} However, if the list ...
11
votes
5answers
306 views

Make a ragged list rectangular by trimming instead of padding

I have a ragged list ragged = {{a,b,c,d,e},{x,y,z}} that I would like to trim (on the right) to be rectangular. The desired result is ...
3
votes
5answers
512 views

Can Mathematica delete some of the 0's from a list?

I have a list: {1,2,3,0,0,4,5,0,0,0}. I want to delete the 0's occurring after the last positive integer. In other words, I ...
0
votes
4answers
55 views

Delete data were y = “NS” in a list with elements {x, y} [duplicate]

I have a list of data {x, y}and not all of them have actual values. They show as {x, "NS"} or ...
0
votes
1answer
33 views

operating lists [on hold]

I have 2 lists 25 items, as I do so that data entering this formula ...
8
votes
6answers
497 views

Flatten nested lists

I have a list as follows lis= {a, {{{b}, {c,d,e}}, {{f}, {g,h,i}}}} which I would like to flatten to ...
14
votes
12answers
607 views

Join lists with nested list

Is there a way of smarter way of joining list of the form l1 = {a,{b,c}}; l2 = {d,{e,f}}; l3 = {g,{h,i}}; To obtain ...
1
vote
3answers
122 views

Deleting one of each chosen elements in a list containing duplicates [duplicate]

I want to delete one of each (and not all) selected element in a list containing duplicates. For example i have the list: $\{1,1,1,2,2,3\}$ and i want to delete $\{1,3\}$ so the leftover should be ...
1
vote
1answer
70 views

What are the terms of the sequence generated by Zeta(3s)/Zeta(s)?

The LiouvilleLambda function has Dirichlet generating function of Zeta[2s]/Zeta[s]. I am curious about an analogous function with Dirichlet generating function of Zeta[3s]/Zeta[s]. Can Mathematica ...
2
votes
2answers
32 views

Count elements between matching opening and closing parentheses?

Suppose I have a List of the form: lst={"(", "x1", "x2", "(", "(", "x3", ")", "x5", "(", "x6", ")", ")", ")"} For each pair ...
2
votes
3answers
86 views

Delete rows based on specific periods

I have data (.xlsx format): two columns - data in first column imported as DateObject (dates with specific time), data in second column are numbers (113388.28, 865165.98 etc.). I want to delete the ...
7
votes
4answers
459 views

Filter list based on date

What I would like to do is remove entries from a list of instrument data when it is in maintenance. The maintenance data I have is a series of dates which look like this; ...
14
votes
8answers
852 views

DeleteCases on list of Strings

Consider the following: data={"AB","CD","AF"}; Now I would like to delete all String from data which starts with "A". ...
0
votes
0answers
34 views

Using lists for creating another list [on hold]

I have list ("F") of numbers of length n. asthma = ((A - B)/A)/Sqrt[XXX], where "A" and "B" are also lists of numbers of length n. The thing I need is that "asthma" will also be a list of numbers ...
11
votes
3answers
651 views

Specifying string patterns in DeleteCases

It seems that DeleteCases is not compatible with string patterns, at least directly (see, for example, this question). Is this true? If so, why is this the case? ...
0
votes
1answer
28 views

Selecting from a list [duplicate]

OK, I know this must be a simple problem, but right now I'm just stuck and need some advice with this :). I have the following list: ...
6
votes
6answers
423 views

Find (longest) overlapping elements between two lists

I am trying to write a function f that returns the overlapped sublist where A ends with this sublist while ...
6
votes
0answers
70 views

TimeConstrained[Delete[Range[1],1]] causes kernel crash

Run these two samples of code here (AFTER SAVING YOUR CURRENT WORK): Do[ TimeConstrained[ While[True, Delete[{1}, 1]; ];, 0.1];, {100}] ...
2
votes
3answers
90 views

Creating sublists based on the first column

I have Excel file consisting of two columns such as: ...
0
votes
2answers
70 views

Block anti-diagonalize a square matrix?

In Mathematica there is a very convenient function called JordanDecomposition[]. It takes a square matrix A as an argument and ...
4
votes
1answer
109 views

Map at a subsequence of a list

I'm trying to construct a function somewhat similar to MapAt. A basic usage example should look like this: ...
1
vote
1answer
53 views

How to extract a contiguous s_1 x s_2 x … x s_d subarray from an n_1 x n_2 x … x n_d array, where the dimension d is a variable

Given a multidimensional array, such as the 3-dimensional 2 x 2 x 3 array { {{a,b,c},{d,e,f}}, {{g,h,i},{j,k,l}} } How can I extract an arbitrary 3-dimensional ...
2
votes
2answers
71 views

Replace missing data

I have vectors of equal lengths where I want to replace the zeroes (missing data) with their preceding values. So far I have written: ...
0
votes
1answer
38 views

Writing a math formula to order results in a certain way [on hold]

I am not very well educated in math and I have a math puzzle that I'm trying to solve. I have the following list and each object has 3 numbers. The first 2 numbers are better when they are as high as ...
1
vote
2answers
90 views

Checker rut for over 7 digit numbers

In Chile the RUT identifier identity, every rut has a check digit module 11 is used, I made this code to 7 digits, but not me 8 digits, a number of 7 digits is the abcdef- form (check digit ) and ...
0
votes
1answer
222 views

How do I plot results of complicated calculations in Mathematica?

I am new to Mathematica and am struggling with making plots of how features of solutions vary with parameters. For example, I can find the eigenvalues and zeroes of a Sturm Liouville problem (showing ...
1
vote
2answers
135 views

How to generate a range of numbers

Is there a quick and dirty way to generate a list of numbers from 1 to some arbitrary large number in order such that the digits of each number are only 0's, 1's, and 2's? I tried doing ...
0
votes
0answers
14 views

Sublist position? [duplicate]

Suppose I have a list of the form: lst = {a,b,c,d,e,f,a,1,5} If I want to find the position of d in ...
0
votes
1answer
50 views

Length of Union Incorrect?

I am having a problem with the Union of sets not giving me the correct Length. ...
4
votes
1answer
138 views

MovingMap maps to second level unexpectedly

I'm trying to build a financial indicator in mathematica. I import some historical data ...
0
votes
2answers
73 views

Exporting a table to Excel in CSV format

I am trying to create a table which when exported in a .csv format and opened in MS.Excel has the following form; ...
1
vote
1answer
39 views

How do you hide/show a dynamic element in a list?

Here is the simplified version of the problem: THIS: {1,2,##&[],4,5} RETURNS: {1,2,4,5} ...
0
votes
2answers
101 views

Making table and plotting results of NDSolve problem

I am trying to solve two equation to find /[Phi][x] and plot h vs. /[Phi][x] for different values of L.I tried by writing as: ...
22
votes
4answers
5k views

Finding Local Minima / Maxima in Noisy Data

I'm trying to find local minima / maxima in noisy data, consisting of data values taken at certain time intervals. Ideally, the function should take a pair of lists (one containing time values and one ...
4
votes
0answers
60 views

FindPeaks finds Minima, but not all of them

I have 10 sets of data, which are the result of measuring the way of a mass falling down over time, bringing a wheel into rotation when the mass hits the ground and then the wheel lifts the mass up ...
3
votes
3answers
87 views