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

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6
votes
5answers
222 views

Multiple level lists

Let there be a list, Sample={{{1, 2, 3}, {a, b, c}}, {{2, 3, 4}, {d, f, g}}} I want to go to individual sublists and do some operation on it.I tried a few things ...
3
votes
1answer
947 views

A rotation-like transform on a matrix

Do not be confused with comments, those are for previous version of the question - Kuba Imagine I have a matrix of the form: ...
5
votes
2answers
322 views

How to group lists that own one common element?

I have produced a list of sub-lists by the following: ...
5
votes
4answers
254 views

Picking numbers within a list with an interval of 60

I have a list of integers from 1 - 400. I choose n random numbers with replacement from the list. Here is an example: ...
9
votes
2answers
472 views

Intersection for lists of numeric data

I know that Intersection is a pattern matching function and will not evaluate list elements to determine if two or more list have equal elements. So my question is, ...
6
votes
1answer
2k views

Mutual Information involving two matrix states

I basically retrieved the following technique of evaluating the mutual information involving two matrices from this site at http://bmia.bmt.tue.nl/People/BRomeny/Courses/8C080/default.htm The ...
8
votes
4answers
568 views

Gather list elements by index

The following list has some elements that are labeled. For example {1, 2} -> 1, {-1, 3} -> 3, etc: ...
6
votes
2answers
248 views

How can I use Pick to select items in one list when a value in a corresponding list is $\leq$ some value?

Imagine I have two lists: List1 = {0, 1, 0.6, 0.5, 1.2, 0.4}; List2 = {"a", "b", "c", "d", "e", "f"}; How can I use Pick to ...
0
votes
2answers
172 views

Create a Matrix out of two matrices

I have two matrices A = {{a1,a2},{b1,b2}} and B = {{x1,x2},{y1,y2}}. I would like to create out of these matrices a new matrix <...
0
votes
0answers
46 views

List elements and iterator name collision [duplicate]

Let there be two lists, exp = {{i, i}, {j, j}}; exp2 = {{r, r}, {o, o}}; and there are two Table commands to access them. Then, ...
11
votes
6answers
395 views

Using MapIndexed only at certain elements of a list

MapIndexed is a very handy built-in function. Suppose that I have the following list, called list: ...
10
votes
5answers
631 views

Span a function across several consecutive elements in a list

Suppose that I have a list called list. I would like to span an arbitrary function f across specified consecutive elements in <...
2
votes
1answer
106 views

Map and Scan ignore HoldFirst

I am trying to write a simple function that takes a list of data and outputs it to a file. I'd like the name of the file to be the same as the variable that holds the list. It seems that giving a ...
1
vote
1answer
155 views

Ways to access lists inside lists

I have gone through some reference material but I am not getting really good links that will help me grow understanding of ...
2
votes
2answers
216 views

Replacing all values in a table > $T$ [duplicate]

I want to generate a table of Euclidean distances from the points in a list to a given point, e.g.: ...
4
votes
2answers
256 views

How can I replace the general element of a geometric series with the sum of the series?

Consider the list mylist = {b(a/bc t)^r, a/b(b t)^r, a (c/d t)^r, ...} where a, b, c, t, etc., are real numbers between 0 and 1. I want to sum each term in the ...
1
vote
1answer
262 views

merge daily and hourly time series data

I have two lists of time series data. One of the lists is daily and is formatted like this; ...
4
votes
2answers
314 views

Multiplying expressions within a list of pure functions

Let's say I have a list of pure functions that are nice algebraic expressions: say l = {(#1 - 1)&, (#1^2 + #1)&, (#1^3 - 1)&} What's an easy way to ...
2
votes
2answers
180 views

Extracting counts of contiguous zeros and ones from a binary array

I'm a novice with Mathematica, but you guys have been very helpful to me in the past. I have a binary array [100, J repetitions] consisting of zeroes and ones. I'd like to extract a histogram of the ...
0
votes
3answers
104 views

How can I generate a generalized product to two lists in a special way? [duplicate]

Let's say I have two lists, and I'd like to generate a "cartesian product" from these two. Specifically Inputs: A = {{{1}}, {{2}}, {{1}, {2}}}; B = {8, 9}; ...
0
votes
0answers
80 views

Importing specific columns of a .txt file [duplicate]

I have text delimited file, with data in four columns. How to use ReadList to extract only the first and the fourth column.
0
votes
2answers
182 views

How to put a list of values on a single axis and add custom labels

I have a table in the following format: Apple 2 Pear 3 Banana 5 Orange 6.5 .... I would like to put the values on a single horizontal axis and add corresponding descriptive labels (apple, pear, ...
7
votes
9answers
532 views

Convert list of lists to cumulative join

I have this: list[1]={1,2,3}; list[2]={7,8,9}; list[3]={15,20,22}; I want this: ...
2
votes
2answers
938 views

Building a new table by repeating elements from another table

I have a small problem that I cannot solve. I have two tables, one with three elements: a = {0, L/c, 2L/c}; and the other with 9 elements, all 0: ...
2
votes
2answers
1k views

Removing pairs that meet a given criterion from a list [duplicate]

Let $(x_{min},x_{max})$ and $(y_{min},y_{max})$ represent lowerbound and upperbound acceptable values for some coordinate $c_i$. Setting $x_{min} = y_{min} = 1$ & $x_{max} = y_{max} = 9$, how ...
-1
votes
2answers
107 views

Extracting only complete records from two data sets and combining them

I have two data sets: ...
3
votes
1answer
203 views

Combining the items with common available dates from two lists [duplicate]

I have two lists of data including dates such as data1 = {{{yy, mm, dd}, a}, ...} data2 = {{{yy, mm, dd}, A}, ...} There are some missing dates from each list, ...
1
vote
1answer
254 views

Bincounting a list

I'm a Mathematica novice here. I'm trying to execute the following code to add random 1's into a zero matrix, repeat this many times, and then bin/histogram the number of nearest neighbor 1s. Can ...
23
votes
7answers
1k views

Elegant and fast way to join all string sequences

I want to do what title says: {"a","b",1,2,3,4,"a",2,2,2,"edg","?"} => {"ab",1,2,3,4,"a",2,2,2,"edg?"} in the most elegant way. For example one replacement rule for ...
11
votes
3answers
423 views

Looking for an elegant way to construct this tensor-product-ish list

I would like to make the following matrix: ...
0
votes
1answer
82 views

How does PolarPlot render a nested list of functions?

I am getting unexpected plots from PolarPlot when I provide a list of functions that I generate using Table. I suspect the ...
4
votes
2answers
984 views

Removing not-a-number entries from an array of numbers

I have a list of {x, y, z} coordinates from a wavefront sensor I'm working with. However, not all of the imported points have actual values, but they still get ...
2
votes
1answer
164 views

list manipulation [duplicate]

I have a list like the following: {{1, 3}, {2, 5}, {3, 6}, {2, 4}} I want the final list to be like that : ...
3
votes
2answers
125 views

Non-canonical re-ordering of nested lists

I have some data in the form: ...
2
votes
2answers
137 views

Select rows of matrix that are higher than a given row

Imagine I have the following matrix: X={{0,0,0},{1,0,1},{1,1,1},{1,2,1},{3,3,3}}. I want to select the sublists that are greater or equal than this list ...
10
votes
1answer
1k views

How can I randomize order of elements in a list?

Is there a straightforward way to go from an ordered list like: ord = {a, b, c, d, e, f, g, h} to a disordered list like: ...
5
votes
1answer
156 views

Assigning Sequence to Part of a SparseArray (bug?)

Part ▪ You can make an assignment like t[[spec]]=value to modify any part or sequence of parts in an expression. ▪ If <...
3
votes
2answers
617 views

Find local maximum in 3D list

I have a set of data of the kind {{$x_i$, $y_i$, $z_i$}, ...} at randomly chosen points $x_i, y_i$. The $z_i$ are supposed to be a smooth function of the $x_i$ and $y_i$. Unfortunately they turn out ...
4
votes
0answers
273 views

Strange behavior of undocumented RawArray and ArrayObject expressions

I discovered several strange results and inconsistencies while trying to understand what undocumented RawArray and ArrayObject ...
1
vote
1answer
514 views

Measuring the area of non analytical regions in a plot [duplicate]

As the title says, I want to measure the area of different closed regions in a plot. Let me be more specific by giving a characteristic example. In the following figure, we observe that inside the ...
2
votes
1answer
232 views

Coarse-graining and/or sorting of a list of arbitrary triades {x,y,z} in the (x,y) plane [duplicate]

In general my question is related to an approach to make an interpolation of a data which is not on a regular mesh. Another aspect of this question has already been discussed after my question "...
13
votes
6answers
725 views

Sort+Union on a list

Probably this is too trivial question for this forum but for some reason I am not getting it on my Mathematica 7 so far. I have a list ...
11
votes
6answers
464 views

Performing Computations on Sets

I would like to find a permutation of $\quad S=\{\frac{1}{10}, \frac{1}{2}, \frac{4}{7}, \frac{3}{5}, \frac{2}{3} \}\quad$ that maximizes the sum of theses elements raised to unique powers: $\;\{0,1,2,...
0
votes
0answers
112 views

How can I revise my program to avoid “No more memory available”? [duplicate]

I have a program for calculating a type of list. ...
1
vote
1answer
144 views

Forming product of function of prime factors

Given a list of numbers each containing 2 prime factors, I wish to make a list of the products of the logs of each factor. For example, given L = {4,6,9}, I would like to form P = {Log[2]*Log[2],Log[...
2
votes
1answer
1k views

Find elements of a list which are empty

Sorry for the most basic of questions. How would I find the positions of a list of elements which are empty, for example I have the list a = {1, 2, {}, {}, 3, 5}; ...
1
vote
1answer
594 views

Simpson's rule with ListConvolve or ListCorrelate

I have a function that's represented as a long list of values that I want to integrate. I can do it procedurally with Simpson's rule. ListConvolve generally runs faster then procedural code, so i ...
3
votes
1answer
169 views

Little problem with Through

list = Partition[Range[20], 5, 5, 1, {}] {{1, 2, 3, 4, 5}, {6, 7, 8, 9, 10}, {11, 12, 13, 14, 15}, {16, 17, 18, 19, 20}} <...
4
votes
1answer
449 views

Equating two lists, element by element

Say you have two lists: listA = {a, b, c} listB = {d, e, f} How would you produce a listC that equates each of the two's ...