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

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2
votes
3answers
521 views

Matlab-style Find in Mathematica? Value list and Boolean List, how to select values according to the boolean list?

I want to select elements with the true value (Indices list) in the corresponding point to the value list (MCS). Is there anything like Matlab-style Find to get the indices of true values in the ...
1
vote
3answers
120 views

ArrayRules for a ragged list

Let there be a sample list as , l = {a, {{b, c}}, {d, e}, {f}, {{g, {y}, u, h}, {{{{k, j}}}}},k, {{{{q}, {w}, {r}, {x}}}}}; ArrayRules[l] ArrayRules::rect: ...
2
votes
1answer
122 views

Putting values into a grid after iteration process

I'm developing a model of thermodynamic cycle in Mathematica. I wrote several functions, applied them to a list containing starting values and iterated, for the model to converge. ...
6
votes
5answers
299 views

Removing reverse versions of lists from a nested list [duplicate]

I need to remove the reverse versions of lists from list of lists. I.e.: {{1,2},{2,2},{2,1},{a,1,2},{2,1,a}} I need to reduce to ...
12
votes
4answers
409 views

Equivalent Nested Loop Structure

Consider the following examples: ...
3
votes
2answers
152 views

Change all values of a series to positive values

I would like to change all values of a series to positive values. I refer to my previous question, answered in the most part, very elegantly by RunnyKine. However, there remains a slight glitch that ...
3
votes
3answers
104 views

Filling in explicit zeros in a (x,y) list for nonexisting y values for discrete Fourier transform in Mathematica

I have a list of (x,y) values in Mathematica for various discrete x values, as in ...
4
votes
1answer
186 views

List manipulation - various

Update OK, Please forgive the messiness of this, but I am working with something like: ...
1
vote
1answer
106 views

Create huge RandomInteger list

For testing purposes, I'd like to create very large amounts of Random Integers, let's say between $-1000$ and $1000$. I'm using the usual ...
0
votes
0answers
28 views

Eliminate some value from a matrix [duplicate]

I have a function that return a table consisting of a 2D points. These points are either {x,y} or {0,0} ...
2
votes
4answers
153 views

Looking for mismatches between two lists

I'm able to do what I need, but it seems like there's always a better way. I have two lists, epiExcel and epiDB. Each has 3 columns and about 2,500 rows. I need to find out if the first 2 columns ...
1
vote
1answer
205 views

Replacement variable in list plot

I would like the replacement: /. {ComplexInfinity -> 0} to be treated as a variable. I am trying to overlay the following list plots: ...
18
votes
1answer
814 views

Two ways of map a function on the list: Which one is faster?

There are 2 ways to make a function listable on the list: Use Map or use SetAttributes. My question is, which one is faster, ...
3
votes
2answers
411 views

How to delete all rows in datafile that contain a string

I'm importing some data from a file. However, the file was created by an unreliable instrument, such that the data looks like this: ...
3
votes
3answers
99 views

How to get different items in a list to interact to get a result?

I have two lists, for example (the real lists are much longer): list1 = {1, 2, 3, 4, 5, 6, 7}; list2 = {9, 10, 11, 12, 13, 14, 15}; I want to create a single ...
5
votes
3answers
201 views

Preserving a bijection between arrays when shuffling elements in one array

Imagine I have two lists of elements like the following: listOne = RandomReal[{0,2}, {100,2}]; listTwo = RandomReal[{0,2}, {100,2}]; Let $f: X \to Y$ be a ...
5
votes
2answers
359 views

Provided an array of 2D point clouds, can we quickly replace distance- and index-based cliques of points with their median or mean values?

Imagine I have $N \approx 10^5$ clouds of points in an array of the form: UPDATED ...
12
votes
9answers
1k views

How to partition a list of numbers in two lists of numbers such that each lists elements sums up to the same number?

I have the following list of squares. {1, 4, 9, 16, 25, 36, 49, 64, 81, 100, 121, 144, 169, 196, 225, 256} Their sum is $1496$, I want to make two partitions ...
4
votes
1answer
205 views

List all possible elements of a set

I have this two sets: $A = \{\emptyset, \{\emptyset\}, \{\{\emptyset\}, \emptyset\}\}$ $B = \{\{x, \{x, y\}\} | x \in A, y \in A\}$ Now I want to list all possible elements that are in $B$. How do ...
0
votes
1answer
48 views

Pruning coordinates in subarrays of a list conditional on them having non-real components

If I have a list of 2D coordinates placed in subarrays of a data structure like the following: ...
1
vote
2answers
657 views

Swapping elements of list

Say I have a directed graph inputted in the following format in Mathematica: g = {{1, "a", 2}, {2, "b", 1}} I'd like to plot this graph using ...
1
vote
2answers
142 views

Quickly pruning elements in one structured array that exist in a separate unordered array

I have two lists, which we'll call testList and modifiedTestList. The first list looks something like this: ...
3
votes
2answers
241 views

Variable length list with # and [[i]] as elements

I need to create a list that as an input receives the number $N$ of elements that it will contain and that returns: ...
1
vote
1answer
154 views

Reading between blank lines in external data files

I have an external data file with several columns and thousands lines of data. For the sake of this question, let's assume that we use ...
4
votes
5answers
298 views

Can I generate a “piecewise” list from a list in a fast and elegant way?

Suppose we have a number list a: n = 1000000; a = RandomReal[{0, 1}, {n}]; We want to generate a list ...
12
votes
4answers
5k views

Removing empty sets from lists

If I had a list, say, names= {"Andy", "Bob", "Carly", "Sandy", "Jeff", "Tim", "Tom", "Zach"} and I decide to pick a characteristic only a certain of them have, ...
0
votes
1answer
360 views

How do you find the longest sublist within a nested list

Say, I have a list stuff={{eat,tea,now},{how,did,you,say},{the,cat,ate,was,can},{win,din,sin}} I have a nested list and I want to find the list that has the most ...
3
votes
1answer
1k views

Plotting multiple lists of complex numbers

The user #Nasser showed an elegant way to plot complex numbers: ...
8
votes
1answer
309 views

Visualizing nested lists for easier human understanding

When interacting with Mathematica, I often find myself staring blankly at waves of curly braces, trying to understand how data is organized hierarchically. For example, the beginning of the result to ...
1
vote
2answers
104 views

Missing something in my input for CountryData dependencies

I'm trying to find (a)which countries have dependencies (b)and a list of countries that consider themselves dependencies (c)and a list of countries that don't consider themselves dependencies. ...
7
votes
1answer
473 views

Efficiently searching a list for the position of the closest number to a specified number

Searching by closest and position I wasn't able to find an answer—but found Nearest by guessing. Nearest, however, returns ...
7
votes
1answer
832 views
8
votes
5answers
396 views

Refer to next element of list when iterating using Map [duplicate]

Is it possible to refer to the next element of the list when I'm using Map or should I always use For in this case? For example ...
2
votes
2answers
226 views

How to replace data in a list (tree) in a functional Mathematica way?

I have list containing 2D points in various groupings, i.e. points, lists of points (figures), lists of lists of points (patterns) and finally a list of patterns. The list also contains other data, ...
6
votes
2answers
177 views

Extract urls from list

If I have a list like list = {"my element 1 http://link.com", "http://link2.com my element 2"} how do I get a list of the links inside each element? Something ...
1
vote
0answers
41 views

How can I access numerical values of variables calculated with Solve? [duplicate]

I am trying to calculate some thermodynamical cycles so I often use lists with equations. Here's a simple example: ...
3
votes
2answers
112 views

Manually accept elements of a list

Let's say I have a list like: {"good element 1", "bad element 1", "good element 2", "good element 3", "bad element 2", ...} I would like to build a function that ...
0
votes
0answers
48 views

How to manipulate lists to get only part of the value [duplicate]

This is really a question about manipulating the output of Maximize. I have a function of 2 variables, defined thus: ...
1
vote
2answers
326 views

How do I find the most populous cities in the world?

I am attempting to plot the most populous cities on a world map. Currently, I have the line of code: ...
4
votes
1answer
172 views

What is the equivalent of MATLAB's “timealign” function?

What is the equivalent of MATLAB's "timealign" function? Given two sequences (lists of values) and offsets, timealign will insert 0's into sequences to align them so they have the same number of ...
1
vote
1answer
239 views

Split Lingustic(IPA) at Words Unique Sounds

How might I split a word at each IPA of each unique sound. For example {"pray", "wade"} (* {{"p","r","ˈeɪ"}, {"w","ˈeɪ","d"}} *) ssch answered a question here ...
6
votes
3answers
217 views

Using PatternTest and/or Condition to detect equal list lengths as well as list element formats

On searching Mathematica.SE for information about overloading functions, I came across several threads about PatternTest and ...
0
votes
2answers
134 views

Where are the functional programming constructs: `every` and `some`? [duplicate]

Coming from other functional programming environments (e.g., Clojure) I've become accustomed to some functions that I haven't found equivalents for in Mathematica yet. The two I reached for last ...
8
votes
3answers
255 views

How to Flatten Array of Arrays of the highest order in a simple way?

I have a matrix of matrices, given in the following code. I want to flatten the array... ...
11
votes
1answer
302 views

How to find longest monotonic sequence?

I have a list, for example list = {2, 1, 3, 5, 4, 6} How to find longest ascending sequence of this list? There are two meanings of this question: Find the ...
2
votes
5answers
298 views

Treat list as cyclic

I am considering the following case. Say that T={p1,p2,p3} represents a triangle. In addition, I want to parameterize the edges of the triangle ...
2
votes
1answer
383 views

How to make an efficient difference of sets function?

How to write a nice code that removes all elements from given set A, that occur also in set B? I would like to use DeleteCases[] for this purpose, but have no good ...
0
votes
2answers
259 views

NestWhile application

I have the function which take the last list in nested list, reduce it somehow in several ways so the length of list reduces and output new list wherein input list appended with defferent reduced ...
3
votes
7answers
413 views

Concise way to generate multiset lists

I wrote the following to generate a multiset with the same number of items over a fixed range: ConstantArray[#, 3]& /@ Range[9] // Flatten ...
0
votes
1answer
221 views

Adding labels on ArrayPlot and coloring rows

I need to add lables on the right from ArrayPlot for each row and color the black square of each row depending on values from two list. Color list has a numbers in some range and should be mapped ...