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

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0
votes
1answer
77 views

Need help to finish this prime signature function?

I'm trying to create a prime signature for line segments. ...
4
votes
5answers
1k views

Dealing with Empty Brackets in a List

I have a large list with varying constituent parts. Some of these are like this: i.e. graphlist[[34]] ...
7
votes
1answer
192 views

Built in way to de-list singletons?

Is there a built in method to de-list singleton expressions, like this rule-based solution: expr_ :> If[Length[expr] == 1, First@expr, expr] In data ...
16
votes
7answers
1k views

How do I check if any element in a list is positive?

As a simple example of what I would like to do, suppose I have a list a of all real numbers. I would like to perform a simple check to see if some element of ...
0
votes
2answers
625 views

How to generate table without comma and bracket or get rid of those?

I want just data without comma and brackets. Even TableForm is not working for me. For example, the general pattern of my table is ...
3
votes
5answers
300 views

How to extract strings from the list with an additional condition on previous elements?

There are a long list of strings $s$ and two lists of substrings $s1$ and $s2$. I want to take all elements of $s$ which contain a substring from $s2$ and such that before it on no more than $n$ ...
3
votes
3answers
153 views

Function[] argument nesting for operations like Select[]

The following code selects a special element from a list thelist = {"this", "notthis"}; Select[thelist, (# == "this") &] What I want is a function which ...
4
votes
3answers
382 views

Adding Lists Together

This is something that should be simple, but the documentation and other questions don't seem to deal with it. I can think of mechanically doing it through a loop, but I know there must be a better ...
7
votes
2answers
1k views

Finding all partitions of a set

I'm looking for straightforward way to find all the partitions of a set. IntegerPartitions seems to provide a useful start. But then things get a bit complicated. ...
10
votes
7answers
210 views

DateList coupled with String Operations

Through some webscraping, I have the following list: ...
2
votes
3answers
222 views

Taking only particular subsets and doing calculations

I have subsets formed from a list using the Subsets command and want to do a particular calculation, lets say subtraction using the ...
3
votes
2answers
218 views

How can the lowest non-zero value in a nested list be found and its position in the sublist returned?

In the example code below we have a list of triples that produce one or more sublists with at least one zero value. How can the positions of the lowest non zero value in each sublist be returned ...
23
votes
6answers
1k views

Mathematica Destructuring

Context I'm writing a function that look something like: ...
6
votes
2answers
318 views
0
votes
2answers
239 views

Calculating average distance

I have a program that gives the average distance as the output. When I tried to repeat finding the average distance 100 times using Table, It failed to generate the output. This is the program. ...
1
vote
2answers
188 views

Expectation over a list with nested-mapped expressions

I need expected values of a list where the random variable to take expectations over should be an input into expressions defined earlier. I suspect Set[] and SetDelayed[] tripped me. (Or Map and ...
2
votes
2answers
1k views

Calculating the distance between the coordinates in a list

I have a list of coordinates {{A[9, 4, 7], 0.0395174}, {A[1, 5, 0], 0.0163797}, {A[0, 7, 2], 0.0577425}, {A[2, 7, 5], 1.01313}} I want to find the distance ...
3
votes
1answer
267 views

Formatting data tables with Grid + Dividers vs. SplitBy --> GridBy?

A quick method to format human-readable data tables with headers, is to use Grid, eg: ...
24
votes
6answers
1k views

How to select minimal subsets?

I am a newbie, so please point me in the right direction if you feel this question has been answered somewhere else before. Here goes: Suppose I have a list like this: ...
12
votes
3answers
1k views

How do I use Map for a function with two arguments?

I'm a newbie who tries to be a good boy, and use Map instead of writing out a list of functions. I have a table I want to Map ...
7
votes
2answers
307 views

Building a tree

Given a list of word characters, such as this one, I'd like to build a tree, similar to this makeTree function, but with the tree in a different format. So, for an input such as ...
10
votes
1answer
497 views

How to monitor the progress of Map?

I have a function doSomethingComplicated[...] that takes about 10s on average to evaluate. My list, listOfArgs has about 10000 ...
3
votes
2answers
1k views

Converting numbers to integers

I've read the available documentation but I still haven't found an NumberForm -> Integer function yet. No result in this site's search, either. Does it exist? ...
4
votes
2answers
943 views

Is there a way to output histogram x and y data without using the Histogram chart function?

I have a large list of data (3.2 million real numbers), and I would like to plot a histogram of it. The built-in Histogram function is very nice, but on my ...
2
votes
4answers
111 views

Obtaining EditDistance[] from a List of Strings

Consider the following question. I have a long selection of files (some 5,000), arranged linearly, and I want to view to what degree the files have changed between each other. For a small example, ...
11
votes
10answers
644 views

Elegant way to map a function to only the last element of each sublist [duplicate]

Suppose that I have the following list, called test: test = {{{a1}, {a2, a3}}, {{b1}, {b2, b3}}, {{c1}, {c2, c3}}}; Now ...
7
votes
4answers
466 views

Prepend 0 to sublists

My question is similar to this one, but my goal is to prepend a single 0 the each sublist, not incrementally many 0's. The file I'm working is a CSV containing around 50K sublists of length 35. I've ...
2
votes
6answers
811 views

Selecting elements from a list one by one

I have an list: l = {{4,5},{7,8},{9,5},{3,2},{1,2},{13,12}}. I want to take the elements in the list in the sequential order. For example the first element in ...
2
votes
5answers
558 views

Assigning a particular value to array elements

I have an array of 10000 elements. I want to randomly assign energy to these 10000 elements using Gaussian or Exponential distribution, such that each time a particular element is selected its energy ...
4
votes
4answers
478 views

Creating lists from a string, separating words from numbers

Say I have a string that contains numbers and words, such as this one: string = "there are 1234 words and numbers 5678 in here $999"; How would I separate the ...
10
votes
5answers
2k views

Best way to create symmetric matrices

From time to time I need to generate symmetric matrices with relatively expensive cost of element evaluation. Most frequently these are Gram matrices where elements are $L_2$ dot products. Here are ...
6
votes
4answers
499 views

Convert head Times to List

I can convert an expression with the head of Times,for example, 12*12.5*13*13.5*14*14.5 to {12, 12.5, 13, 13.5, 14, 14.5} by ...
17
votes
3answers
721 views

Using pure functions in Table

I need a table with the elements made of pure functions and list elements. This is a simplified example: I need a list as: ...
4
votes
1answer
331 views

Using Partition to allow sublists of different lengths

As a minimal example, suppose I have a list of the integers from 1 to 25. Suppose I want to use Partition to partition the list into sublists of length 10 but ...
4
votes
1answer
323 views

Change elements on different positions within a list

How can I change the elements of a list, say on positions {{1, 4}, {3, 1}, {2, 3}, {4, 4}} in one go? Take this list for example: ...
9
votes
4answers
514 views

Using Position (which requires a pattern) in the same manner as Select (which requires a criterion)

I am using Mathematica7. I have a list of lists (creatively named list in the following sample code) containing data. I would like to find the positions of the ...
21
votes
4answers
1k views

Sort lists according to the order of another

I have three parallel lists (i.e. the elements in position i of each list are related). I want to sort the first list using the function Sort and make the same changes to the other lists so that I ...
1
vote
2answers
327 views

Operations on sets of sets [duplicate]

Possible Duplicate: How can I remove B -> A from a list if A -> B is in the list? Delete duplicate elements from list Pattern matching deletion of list items How do I delete the ...
6
votes
5answers
383 views

Computing the equivalence classes of the symmetric transitive closure of a relation

I have a list of pairs, for example: ...
2
votes
3answers
538 views

Recursive function on list

Please consider the following: I have to deliver the weekly customer demand data on time. I can start to produce my products one week in advance. So I was thinking ...
32
votes
5answers
2k views

Partitioning with varying partition size

How can I partition a list into partitions whose sizes vary? The length of the $k$'th partition is a function $f(k)$. For example: if $l = \{1, 2, 3, 4, 5, 6\}$ and $f(k) = k$. Then the partitioning ...
16
votes
3answers
3k views

K-means clustering

In MATLAB, there is a command kmeans() that divides an array into $k$ clusters and calculates the centroid of each cluster. Is there any command in Mathematica to ...
5
votes
2answers
364 views

From a list of dates get a list of the last date available in a each month

I wondered if anyone has another or even a more direct way of finding the last dates of each month available from a list of successive dates? I currently do the following (note: nothing special about ...
4
votes
1answer
154 views

Sorting a list and finding an array of indices that sorts the list

How can I sort a list and also get a list of indices that sort this list? For example: primary list is a a={1,4,6,7,0,2}; sorted list is b ...
2
votes
1answer
262 views

Table with dependent iterator

I'm trying to build a table where the iterator is based off of the ith-1 entry in the table. In other words, the value at i is based on a function with i-1 as its input. EXAMPLE: Let's assume we're ...
3
votes
1answer
206 views

Exchange axes in ListLinePlot

I'm sorry to do this right off the bat, but I have the following set of data: ...
12
votes
7answers
831 views

How to Set parts of indexed lists?

I would like to assign a list to an indexed variable and then change it using Part and Set like this: ...
6
votes
3answers
675 views

Generating a non-convex polyhedron from a list of vertex coordinates

I want to include a figure in a paper I am writing on Combinatorial Geometry which features a non-convex polyhedron given by the following vertices, EDIT: I was unaware that Mathematica could convert ...
2
votes
2answers
283 views

Pattern test for variables during function definition

I am having a problem with pattern testing on variables during function definition ...
5
votes
1answer
121 views

RankedMax and Max do not behave identically

I have spent three hours debugging some code and at the end I think I found a bug. Otherwise I cannot explain what I am seeing: When I want to use RankedMax on ...