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

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3
votes
1answer
131 views

Filtering the elements of an array to split them into two categories

So, I am new to Mathematica, and I am trying to write something that involves taking values from one array and separating them into two different arrays. My code for doing this is: ...
3
votes
1answer
259 views

Replace elements in a list

Suppose that I have a list: ...
3
votes
2answers
93 views

How to generate a list from an iterator and some arbitrary function

Suppose I'd like to generate a table of integers: Table[i, {i, 10}] Great; now suppose I want only the integers that are even ...
3
votes
1answer
279 views

Operations on a List of Vectors (Norm)

I have a List containing vectors. The coordinates are random numbers: r = {RandomReal[{-1, 1}, n], RandomReal[{-1, 1}, n], RandomReal[{-1, 1}, n]}; Now I want to ...
3
votes
3answers
80 views

Generating increasingly longer lists from a single list

I start with an array such as {{1,1},{0,1},{-1,1}}. (1) I want to create an array from this which replaces each array inside the array with 3 new arrays, one ...
3
votes
1answer
74 views

Remove values from list element, and add to other element

Basically what I need is to make a list of 400 elements, all have value 1. The next step is to create a function, that subtracts value (-1) from an element, and adds that to another element. So: ...
3
votes
1answer
114 views

Read and write files

I have a text file, its content is(for example): ...
3
votes
2answers
105 views

Find Lists with intersecting sublists

I have a list of the following form: ...
3
votes
1answer
652 views

Plotting multiple lists of complex numbers

The user #Nasser showed an elegant way to plot complex numbers: ...
3
votes
1answer
436 views

Exporting/Importing a Table of complex numbers

I'm generating a long table of list of the form: PN={{1,2,1+i},{3.5,2.6,2}...},{...},... Using: Export["PN.dat", PN, "Table"] ...
3
votes
2answers
595 views

Dynamically remove element from list based on test

Suppose I have a list l = {a, b, c, d, e, f....} I would like to remove one of each pair {x,y} if some function ...
3
votes
2answers
169 views

Modify all the second elements of every pair in a list of pairs

I have a list in the form {{a, 1}, {b, 2}, {c, 3}}. Let's say I want to operate a transformation on all the second elements of each sublist, but this transformation is a function of them all ...
3
votes
1answer
207 views

Indexing of Large Autonomous System of Equations for Use in NDSolve

I currently have a list of ~150 autonomous ODE's that I need to be able to work with using NDSolve. Fortunately I already have them formatted in plaintext, which ...
3
votes
1answer
193 views

Efficiently finding the maximum value of a column in a matrix

Imagine I have a matrix of the following form: TestArray = $((a_1,b_1,...),(a_2,b_2,...),(a_3,b_3,...),...)$, where a specific example might be: TestArray = ...
3
votes
0answers
80 views

Why does Part behave like it transposes lists? [closed]

From the documentation of Part: Part[expr,i,j,...] is equivalent to expr[[i]][[j]]... ...
3
votes
0answers
281 views

Taking real and imaginary parts of indexed functions and speeding up ComplexExpand

I am setting up a large system of ODEs and in order to use the IDA method (which is sig. faster for my system and thus attractive), I must split my equations into real and imaginary parts. I am ...
3
votes
0answers
97 views

Gather dependency on list order?

I get intrigued about Gather behavior on this post. I thought that Gather was invariant under list order? Here is the result I ...
3
votes
0answers
67 views

Listing all combinations produced by picking one element from each of several sets [duplicate]

I have a problem like this, I am given the following sets {a,b,c}, {d,e,f}, {h,i,j}. I want to pick one element from each set, and output a list of all the ...
3
votes
0answers
150 views

List manipulation, replace a value [duplicate]

I have the following list: ...
3
votes
0answers
188 views

Exporting Specific Cells of Many Workbooks into One using Mathematica

I currently have a large number of detailed files from which I would like to extract certain cells' information to make an Archive spreadsheet. There are approximately 9 parameters of each ...
2
votes
6answers
1k 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
3answers
279 views

Create a list of random reals

How can I create a list of random pairs $(x,y)$ where $0<y<x<1$ and $x,y \in \mathbb{R}$ ? I can't seem to place that inequality restriction on the random numbers that are generated.
2
votes
3answers
633 views

Problem with Union and Intersection

Consider the following: list={{a,b,c},{c,d,e},{d,e,f},...{x_,y_,z_}}; I would like to apply Union on the elements of the list ...
2
votes
3answers
252 views

Picking items from a list

There's probably a Mathematica primitive to do this, but I don't know what it is...suppose I wanted to construct a list of all integers from $1$ to $n$ that were not divisible by $12$, and that were ...
2
votes
5answers
219 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
4answers
224 views

Get 'new' list of data by manipulation 'old' list

Assume I have the the following list of data: valuesOld = {5, 10, 15, 20, 25, 35, 40, 45, 55, 65, 80}; I would like to construct the following list: ...
2
votes
4answers
381 views

Building a list recursive with one or more arguments

Consider the following: data={a,b,c,d}; res={{a,b,c,d},{b,c,d,e},{c,d,e,f},{d,e,f,g}}; The idea is to define a function ...
2
votes
4answers
112 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, ...
2
votes
6answers
215 views

Manipulating List

I have a list: b={{1, 1}, {2, 2}, {3, 3}, {5, 5}, {6, 6}, {8, 8}, {10, 10}} I want to insert the elements in this list: ...
2
votes
4answers
221 views

How to improve the quality of the ListPlot output

I need to plot massive data stored in external ASCII files. Below is the Mathematica code I use for this job: ...
2
votes
3answers
2k views

How to convert output of a For loop into a list

I have written a For loop in my Mathematica notebook. This For loop, when activated, will generate a sequence something like: ...
2
votes
3answers
315 views

How to transpose unequal lists

As the titel says I want to transpose a matrix containing rows of unequal length, to be able to transport them to excel (in row form, there are too many datapoint to write them in a cell. In another ...
2
votes
2answers
260 views

Position function not always retuning an answer even with no apparent problems

I'm having some problems with Position. Sometimes it will give an empty list instead of the actual position of the element I am looking for when that element is ...
2
votes
3answers
192 views

Rearrangement of the list

I have the following list: ...
2
votes
3answers
211 views

appending element to sub list [duplicate]

I have a list of the form: lstA = { { {"a","b"}, -1.5}, { {"c","d"}, -2 } } I wanto to add another value to each sublist that ...
2
votes
3answers
307 views

Re-arranging / selecting of a data table very slow in For loop [duplicate]

My task is quite simple; I have a table of data like M = {{1,2}, {1,3}, {3,4}, {5,1}, {6,9}, {6,8}, {6,1}}; so the table is sorted with respect to the first ...
2
votes
7answers
333 views

How to replace plus sign by comma

I want to replace plus by comma and the order of numbers in the list should be in increasing order. Example: a1 + a10 + a11 + a13 + a2 + a27 + a28 In this ...
2
votes
4answers
818 views

List manipulation: position & max value combination

Starting with {{0, 0, 0}, {1, 1, 2}, {2, 3, 3}, {3, 4, 5}} I would like to get {{0, 2, 3, 5}, {1, 3, 2, 3}} where the ...
2
votes
4answers
220 views

Removing coefficients and repeated elements

I got to a problem where as I just can't find the proper Mathematica command. I'm given a list, for example: $\{1,x1,-x1,x2,x5,x3,-x2,-x4\}$ I need this to become $\{1,x1,x2,x3,x4,x5\}$ The ...
2
votes
3answers
519 views

Selecting subsets of a list containing a specific element

I'm trying to generate all the subsets of a set containing a specific element. For example, for the set {1, 2, 3, 4}, with the specific element I want inside each subset being 4, the required answer ...
2
votes
2answers
135 views

How to apply # on different lists? [duplicate]

If I have list1 = {1, 2, 3, 4} list2 = {5, 6, 7, 8} How can I do so, that function[#1, #2] takes ...
2
votes
3answers
196 views

Alternatives to Append/AppendTo for generating a list in an interactive DynamicModule?

I have a stack of timelapse microscopy images that I am trying to segment frame-by-frame using some of Mathematica's image processing functions. I have created a little interactive DynamicModule with ...
2
votes
4answers
743 views

ListPlot multiple datasets over same x-values

Is there a better way to enter my data into a list plot? ...
2
votes
2answers
157 views

Comparing elements of the $n^{\text{th}}$ sublist in a ragged list with the $n^{\text{th}}$ member of a sequence

I have a list of lists that are not of the same length (for example, {{6}, {14}, {6, 26, 30}}), but I have to compare every element in the $n^{\text{th}}$ sublist ...
2
votes
3answers
633 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 ...
2
votes
4answers
164 views

How to remove hours, minutes, seconds from list

How to remove 0 that represent hours, minutes, and seconds from a date list say a ...
2
votes
2answers
153 views

How to get the current index during a Scan iteration?

Is there a special keyword to get the current index in Scan ? For example, let say I have the following code : ...
2
votes
3answers
152 views

How to display the indices/element positions of a ragged array?

I have a three-level ragged array like so: ...
2
votes
2answers
102 views

What is wrong with my use of Flatten? [closed]

Why does Flatten[f[g[a, f[b]], f[c, d]]] result in f[g[a, f[b]], c, d] I expected the answer to be ...
2
votes
3answers
184 views

Using Part rather than Extract

In my work I found that I needed the Extract function. However I was wondering if there was a way to use Part. Assume that ...