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

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2
votes
3answers
847 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 ...
49
votes
5answers
3k 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 ...
26
votes
4answers
5k 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
562 views

From a list of dates, get a list of the last date available in 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
189 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
341 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
237 views

Exchange axes in ListLinePlot

I'm sorry to do this right off the bat, but I have the following set of data: ...
13
votes
7answers
1k 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: ...
7
votes
3answers
1k 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 ...
4
votes
2answers
435 views

Pattern test for variables during function definition

I am having a problem with pattern testing on variables during function definition ...
5
votes
1answer
131 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 ...
14
votes
4answers
912 views

Implementing a function which generalizes the merging step in merge sort

One of the key steps in merge sort is the merging step. Given two sorted lists sorted1={2,6,10,13,16,17,19}; sorted2={1,3,4,5,7,8,9,11,12,14,15,18,20}; of ...
38
votes
3answers
1k views

Tiling a square

I wondered if there was a way to automate the process of finding a way to tile a tile into a square. The idea is to represent the tile with a matrix of $0$s for blank space and $1$s for filled spaces ...
9
votes
3answers
367 views
20
votes
9answers
2k views

How do you check if there are any equal arguments(even sublist) in a list?

I would like to set up a function which has to return True if at least two arguments of a given List are equal. So if I give {1,4,6,2} to the function it has to ...
17
votes
4answers
508 views

Splitting a list

Please consider the following list: data={1, 0, 0, 0, 2, 5, 2, 3, 0, 0, 3}; Now I would like to split the list into 0-sequences and Not-0-sequences as following: ...
2
votes
1answer
1k views

Indices and variable definitions in Mathematica

Does anyone know how I can do this in Mathematica? Just an example.. Defining indices and variables (defined over indices), "mapping" variables and indices: ...
10
votes
3answers
912 views

Count consecutive positions with the same value

I want to program a function that counts the successive positions with the same value: In[]= ConsecutiveValues[{1, 1, 1, 1, 2, 2, 1, 0}] Out[]= {4, 2, 1, 1} In ...
7
votes
3answers
171 views

List has a date and amount, I need to create a cumulative amount by date

I have a list which has a date and a amount, I need to create a list that has the cummulative total with the date. I have the following result: ...
6
votes
2answers
333 views

How to choose variables from a list for a function and then use the solution in a subsequent function?

I am trying to calculate heating degree days and cooling degree days and output that information to a table. I am using mathematica's curated data to do this. In text this is what I would like to ...
6
votes
3answers
665 views

How to take part (and then sum over) of specific level of an array?

Specifically, I want to take some elements of the lowest level of an array, and then sum over these elements while holding the higher level. Sorry for my vague expression, maybe an example would make ...
8
votes
2answers
412 views

Retrieving duplicates from nested list

Consider the following: data={{1,a},{10,a},{5,b},{4,c}}; In my case duplicates are defined when for {x1,y1} and ...
31
votes
4answers
766 views

How to make MapAt work with Span?

Span (;;) is very useful, but doesn't work with a lot of functions. Given the following input ...
14
votes
4answers
398 views

MapThread with non-rectangular lists

MapThread works fine and dandy with rectangular list structures: MapThread[f, {{{a, b}, {c, d}}, {{1, 2}, {3, 4}}}, 2] ...
9
votes
2answers
1k views

Rapidly binning 3D data

I have a set of data (about 20 million datapoints for my real data) of the form {x, y, z, m}. There are 3 spatial coordinates x, ...
10
votes
2answers
342 views

Using Gather to rearrange my data

I have a list of elements: {{1, 2}, {1, 5}, {2, 6}, {3, 7}, {4, 8}, {5, 6}, {5, 9}, {9, 13}, {10,11}, {11, 12}, {11, 15}, {15, 16}} I have to divide it into ...
4
votes
4answers
432 views

Add/replace a rule in a list of rules based upon the rule's lhs without regard for the rule's rhs

I have the following lists of rules: {x -> 1, y -> 2} {x -> 1, y -> 2, z -> 4} {x -> 1, y -> 2, z -> 2} For each list of rules, I would ...
12
votes
3answers
851 views

Delete duplicates in a list, depending on the sequence of numbers

Below, list is a representative sample of my list, which contains lists of integers. I would like to be able to input: ...
2
votes
2answers
143 views

Using FreeQ with implicit functions

In Mathematica 7, I want to determine whether a list of free of numbers greater than 1 or not. It seems like using FreeQ would be a concise way to do this: ...
5
votes
4answers
457 views

Leveling peaks in list

Consider the following: data={2,2,2,5,3,3,3,6,1,1,1,0}; In[1]:=result=MyFunction@data Out[1]:={2,2,3.5,3.5,3,3,4.5,4.5,1,1,1,0} ...
14
votes
3answers
602 views

Determining all possible traversals of a tree

I have a list: B={423, {{53, {39, 65, 423}}, {66, {67, 81, 423}}, {424, {25, 40, 423}}}}; This list can be visualized as a tree using ...
23
votes
11answers
634 views

Using MapAt to map at a particular depth (levelspec)

I have the following sample list (my actual list is, of course, much longer): ...
5
votes
2answers
688 views

Add elements in a sublist

I have created a subset of arrays: ...
6
votes
2answers
3k views

Is it possible to compute with the trapezoidal rule by numerical integration?

Is it possible to compute trapezoidal rule numerical integration? I know that Mathematica has Interpolation, and that a list of points can be interpolated and then ...
25
votes
2answers
2k views

Populating and storing a very large array in Mathematica

I am using Mathematica 8 to generate a very large multidimensional array of floating-point numbers and then store it in a file. Typical array sizes are 10000 x 50 x 15 x 40, resulting in a 3-4 GB ...
7
votes
4answers
457 views

Evaluating a function using arguments from a sliding window over a list [duplicate]

Possible Duplicate: How to Map a subset of list elements to a function? I want to evaluate a function using arguments from a sliding window over a list. As an example, lets use ...
11
votes
4answers
4k views

What is the cleanest way to prevent divide-by-zero warnings?

If I evaluate {1, 2, 3, 4}/{5, 6, 0, 8}, obviously I get one warning: ...
9
votes
4answers
861 views

Filter a list generated with Tuples

I generated with Tuples[{{1, 2, 3, 4, 5}, {1, 2, 3, 4, 14}, {1, 2, 3, 4}, {1, 2, 3, 4}, {1, 5, 6, 7, 8}, {5, 6, 7, 8, 10}, {5, 6, 7, 8}, {5, 6, 7, 8}}] ...
5
votes
3answers
255 views

Point belonging to a Disk in a Cartesian Coordinate System

The image below represents a human subject fixations while observing this abstract pattern for 3 seconds. I would like to know how much time they spent looking at the actual disk. That is a red point ...
6
votes
3answers
764 views

Subsets of a list

Consider the following demand of products for the next four months. data={1,20,3,40}; I could produce the whole demand in the first months, leading to the ...
-1
votes
3answers
405 views

Combining lists

How can I combine list1={{x1,y1},{x2,y2},{x3,y3}} and list2={{x4,y4},{x5,y5}} to ...
10
votes
3answers
903 views

Splitting a list at a particular position

Is it possible to split a list into two lists at a specific position? The main list is for example: data={{xa,ya},{xb,yb},{xc,yc},...,{xz,yz}}. I want to split ...
1
vote
3answers
201 views

How can parts of a list of lists be printed to the nb, at regular interval positions?

I have a large list of lists with the dimensions {441,21,21,3} of which I need to print the x,y,z data from every 21st part up to 441. How can I print the 21x21x3 piece of every 21st part of this ...
1
vote
2answers
299 views

Recursion on a moving window

I need to apply some computations to a moving window of $N$ items in a time series and I am struggling with doing recursion and shifting the considered window. To illustrate, please consider the ...
4
votes
3answers
331 views

Counting elements skipped using Reap & Sow

I am using the following code to filter data based on the percentage change between points. ...
6
votes
1answer
654 views

Finding all length-n words on an alphabet that have a specified number of each letter

For example, I might want to generate all length n=6 words on the alphabet {A, B, C} that have one ...
23
votes
3answers
525 views

Is there a bug in Pick?

I wanted to use the Pick function with a condition. But there seems to be an issue here. Take a look at this: ...
9
votes
8answers
785 views

Adding elements to a collection of lists

I would like to add element a at the start of a series of lists. For example I have a collection of lists called ...
6
votes
3answers
1k views

print the name of the variable in a list without evaluation

a := az + 1 b := bz + 5 list := {a, b} I'd like mathematica to print a = az + 1 b = bz + 5 so basically it needs to first ...
14
votes
5answers
620 views

Interlacing a single number into a long list

This seems like it should be a simple question, but I am running into some difficulty in doing this with Mathematica. Right now, I have a list like this: ...