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

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5
votes
3answers
221 views

Count elements of a list

Let's create a random list n = 100; data = Table[{RandomReal[{0, 2}], RandomReal[{-1, 1}]}, {i, 0, n}] Now we divide the $(x,y)$ plane into four sectors with the ...
3
votes
1answer
191 views

How can i subtract a surface from another

I have one surface which i got with using analytical solution. And one by ListPlot3D. My question is how can be withdrawn from the one from the another. ...
0
votes
1answer
122 views

Manipulating list based on Euclidean distance

I have an array of 101 matrices. Each matrix contains information like id, position (x,y,z), time etc about a collection of particles, looks like this ...
1
vote
1answer
94 views

Summing terms in Table

I have a table that looks like Table[m, {k, 10}, {j, k}, {i, j}] where, m is a square matrix that depends on the indices $i, ...
1
vote
2answers
76 views

Circular Playing up in a Grid

As we know, there is a possibility to emphasize some elements of a Grid by highlighting its cell with ...
8
votes
4answers
751 views

Replacing a for-loop with something functional

I'm a physics grad and have been using Mathematica mostly for data visualization. The evaluation part I normally do with C/Python, but I've been wanting to try out Mathematica for these tasks, too. ...
2
votes
3answers
136 views

How to insert a Matrix into a larger matrix

I have a 4x4 matrix v1 v2 v3 v4 myM={{a1,a2,c1,c2}, v1 {a2,a3,c2,c3}, v2 {c1,c2,d1,d2}, v3 {c2,c3,d2,d3}} v4 And I want to ...
3
votes
2answers
85 views

Combining sub-matrices by replacing zero elements with symbols

I have a nested matrix as m: ...
6
votes
6answers
233 views

How to check if two nested lists have the same structure?

How can I check if nested lists like these have the same structure: ...
3
votes
2answers
77 views

SameTest issue?

Folks, I am trying to construct and algorithm which finds all of the remaining groupings (of three items, in this case) from a list of items for which no two items are in groups that have previously ...
1
vote
2answers
54 views

Filling a matrix with a list of lists

I have a list of lists with different lengthes: {{a1,a2},{b1,b2},{c1,c2,c3},...} Now I want to create a matrix the following way: ...
0
votes
1answer
70 views

Unexpected results from output with NumberForm and ScientificForm

I wrote this little function to help me export tables with formatted numbers to files: (By the way, if you have suggestions on how to make it more efficient and compact, it would be great) ...
3
votes
2answers
298 views

Convert a list of hexadecimal numbers to decimal

I know that to change a single number from hexadecimal representation to decimal, you can use: base^^digits. However, if you have a list of numbers, Mathematica ...
2
votes
2answers
66 views

How to apply list of values to a list of functions

I have the following: first= {1+a,2+a,3+a,4+a} and a list t={0,1,2,3} I want to evaluate the first element of "first" at ...
9
votes
2answers
472 views

How do I prune a list of pairs of numbers so that each number occurs on only one pair?

How do I select only the first pair of numbers in which a number occurs from a list of pairs of numbers? For example, I have ...
1
vote
1answer
59 views

Delete duplicates from list of pairs

I'm fairly new to Mathematica, and I've finally stumbled upon something that's beyond my googling powers. I have a list of pairs, where each pair contains in its first entry a matrix and in its ...
4
votes
2answers
96 views

Select sub-lists of common length from a list

Revised Question I have a list with nested lists with the following format: ...
0
votes
1answer
28 views

How to combine two or more groups while selecting form the unbalanced panel data if the number of obs is less than a scalar in certain groups

I have an unbalanced panel data. I want to calculate group statistics for each group. However, if ith group has less than K obs, then I want to combine ith and (i+1)th groups to calculate group ...
13
votes
7answers
765 views

How to sort digits in a string while keeping other characters untouched?

Now there is a string with digits and letters, for instance, "95uge678r3gi89hgfe30kgh063d51". And the expected output is ...
4
votes
5answers
263 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 ...
8
votes
3answers
377 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
80 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
74 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 ...
4
votes
2answers
110 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 ...
0
votes
0answers
24 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 ...
1
vote
3answers
65 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
1answer
60 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 ...
6
votes
2answers
132 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
1answer
37 views

operating lists [closed]

I have 2 lists 25 items, as I do so that data entering this formula ...
13
votes
1answer
161 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: ...
5
votes
6answers
590 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 ...
1
vote
1answer
41 views

Change date format in nested lists

I have a list of index symbols and data as follows: ...
1
vote
3answers
141 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 ...
2
votes
2answers
35 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 ...
0
votes
4answers
66 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 ...
9
votes
6answers
549 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 ...
2
votes
3answers
146 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 ...
0
votes
1answer
32 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: ...
3
votes
2answers
120 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
2answers
76 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 ...
0
votes
1answer
38 views

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

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 ...
6
votes
6answers
452 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 ...
8
votes
0answers
106 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}] ...
1
vote
2answers
148 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 ...
1
vote
2answers
116 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 ...
2
votes
2answers
87 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
0answers
16 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
51 views

Length of Union Incorrect?

I am having a problem with the Union of sets not giving me the correct Length. ...
1
vote
1answer
91 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 ...
0
votes
2answers
105 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; ...