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

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2
votes
2answers
241 views

Efficient code for building a big list

I would like replace the following code ...
0
votes
1answer
172 views

DataRange problem in a ListLinePlot within a Manipulate

I'm trying to create a simulation of a set of lists with Manipulate[] and ListLinePlot[]. However, as my simulation starts with ...
2
votes
5answers
226 views

Creating ordered triplets from an Excel sheet

I have an Excel sheet of the form: " " a b c 1 R S T 2 U V W 3 X Y Z Where every entry is a number (except the blank quotes, ...
0
votes
0answers
45 views

DeleteCases and Inequalities [duplicate]

I would like to remove cases from a list according to an inequality rule - e.g. remove all values less than x. I can do the following but this seems very clumsy: ...
2
votes
2answers
255 views

How to prevent errors in Manipulate with ListPlot when a result is an empty list?

I am trying to plot two lists, where one is the reference list, and the other is only used to select and highlight the first list. Basically, I want to use the selection list ...
4
votes
5answers
594 views

Removing zero values from ordered pairs

I have some processed data, which are basically a collection of ordered pairs in the form: {{x1, y1}, {x2, y2}, ..., {xn, yn}} Ordered pairs which have either a ...
14
votes
6answers
517 views

Matrix Rotation

If I have a matrix of any size, say $\begin{pmatrix} 72 & 32 & 64 \\ 18 & 8 & 16 \\ 63 & 28 & 56 \\ \end{pmatrix}$ $\begin{pmatrix} 72 & 32 \\ 18 & 8 \\ 63 ...
1
vote
2answers
119 views

Speeding up a simple simulation with random extractions

I wonder if anybody can help, I need a hand with a simple simulation I am writing with Mathematica (I am using version 8). Basically it creates a list (called l) with numbers from 1 to n and a random ...
5
votes
2answers
182 views

Better method for creating a tuple out of two lists

I just combined two lists using this method ...
1
vote
2answers
68 views

How to construct a new list made from a function that operates on two lists

I need to take two lists (each list contains the number of moles of a chemical). I have a function calledFraction that takes the each entry of the list and then calculates the mole fraction of ...
1
vote
2answers
196 views

List of numbers without common factors with a certain number

Is there any function in Mathematica which directly gives an array of integer numbers with no common factor with a certain integer number? For example, all the integer numbers between 0 and 1728, ...
-1
votes
2answers
312 views

Convenient methods to sum select rows (or cols) of a matrix? [duplicate]

What are some convenient methods to sum selected rows or columns in a matrix? This question Summing along rows or columns of a matrix only addresses how to sun entire rows or columns ie, by level. ...
5
votes
1answer
141 views

Trouble with Flatten[]

I made this function: f[g_] := Table[{ToExpression[ToString[x] <> ToString[n]], 1, 3}, {n, 1, g}] When I evaluate the function with some g (say 8), I'll ...
1
vote
2answers
198 views

How to blend some colors on a curve

I need to define a color gradient on a 3D curve, but I'm having some problems with this. Suppose we have a 3D curve defined as a parametric function of some real variable ...
16
votes
4answers
470 views

Accessing list elements by name

First, a bit of a long introduction to my problem: I only have a few weeks of Mathematica experience. I am creating a mathematica application that calculates some material properties of steel based ...
5
votes
1answer
151 views

Can the elements of a list always be sorted into a canonical order?

As the title states - does a unique order exist for any Mathematica list to be sorted by the Sort[] function (or as returned by a function that treats lists as ...
4
votes
1answer
127 views

How do I group a nested list further according to a rule, and average selected elements?

I have a nested list of numbers like { {36, -244}, {37, -225}, {38, -197}, {48, -200}, {49, -181}, {50, -133} } which needs to be further nested into "bins" according to a rule. I would describe the ...
-1
votes
1answer
134 views

How to change the value of an array that is outside the For loop, from inside the For loop [closed]

H is a square matrix which depends on the vector d which I define below. I redefine d in each iteration but I need to plug it in H in each iteration aswell. It is easy if I define H inside the For ...
10
votes
4answers
325 views

How to add lists with unequal length?

Given lists of unequal lengths, I want to add them together element-wise, treating missing elements as zero. For example, {1, 2, 3} + {a, b} + {x} should give ...
3
votes
2answers
132 views

Creating a list from other lists and varying the number of elements that get added

Suppose I have listA = {M, F} and ListB = {a,b,c} I want to make a new ...
0
votes
1answer
117 views

Using a loop to make a new list by taking elements from multiple lists [closed]

I have defined three lists and I need to be able to take elements from them periodically and put them in a new list. I know I need to use some form of a loop but I am at a loss. Any suggestions?
0
votes
1answer
95 views

How to extract data from a list? [duplicate]

I have a long list of coordinates defined in some 8D space. I need to extract the first three coordinates only. How ? For example : ...
4
votes
2answers
335 views

List reversion inspired by Python

In python, if you wish to reverse a list, here is the trick: range(10)[::-1] => [9, 8, 7, 6, 5, 4, 3, 2, 1, 0] Note: ...
3
votes
1answer
177 views

How to store values indexed by integer partitions for fast access?

I have a huge list of values indexed by integer partitions. If I store them simply in a list, then, when I want to access the value corresponding to some particular integer partition, I have to find ...
-7
votes
5answers
387 views

Translating MATLAB's cell2mat into Mathematica

How I can define a function in Mathematica such that it acts same as the cell2mat command in MATLAB? Example (in MATLAB): ...
1
vote
2answers
348 views

How do I divide the columns of a matrix by the sum of its elements?

I am trying to create a transition matrix for a network. In order to do this, I need to sum down the column (the out degree), and then divide the column by the out degree in order to normalize it. ...
0
votes
1answer
115 views

Dynamic List Building and Exporting [closed]

My ultimate goal is to have a text file that contains the following information in the following format exported to a text file: ...
0
votes
2answers
119 views

ListPlot of lists with specified x coordinate

I want to do: ListPlot[{{x1, y1}, {x2, y2}, ...}] each y being not a number but a list of numbers. I tried: ...
4
votes
2answers
237 views

Sorting a matrix alphanumerically

Somewhat related to Sort matrix by columns and rows without changing them, but more general. I'd like to sort a square matrix (a 3 by 3 in my case, but surely the general solution will treat any), ...
3
votes
3answers
193 views

How can I name “a[[i]]” the parts of Table “a”? Or how to make Table “a” grow inside FindMinimum?

Let's say I want to minimize a function that uses a Table named a with the Conjugate Gradient Method of ...
3
votes
2answers
431 views

Adding and subtracting from elements in a list

I'm trying to solve an aparently simple problem. Given a list of length n, {a1,b1,c1,d1...} I want to perform two simple ...
8
votes
4answers
137 views

Mark selected sub-lists in the list they were selected from

I've got this simple problem with two lists. I select some items from a list, but I want to visualize the difference between the previous list and the list that I create with ...
9
votes
5answers
627 views

Building a continued fraction

I've completed a problem that involves approximating $e$ by a continued fraction: $$\frac{N_1}{D_1+\frac{N_2}{D_2+\frac{N_3}{\ddots+\frac{N_k}{D_k}}}}$$ with the $N_i$ being the list ...
2
votes
2answers
239 views

Preparing data for making an ErrorListPlot

I often have the following notebook in Mathematica, which I use to make a dataset and associated errors: ...
1
vote
3answers
288 views

Convert coefficients of polynomials into a matrix

I have several sets of 5 polynomials of the form: ...
1
vote
1answer
68 views

How can I use list processing functions on data in a file?

How might I work with the following functions on a list, if the list is a disk based file? Partition[] DeleteDuplicates[] Split[] SortBy[] The file is too ...
3
votes
2answers
89 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
2answers
241 views

Colors associated to parts of a 3D distribution of points

Suppose we have a long list of random points (cartesian coordinates) in 3D space. coords := ...; Until now, I was associating colors in a radial way, from the ...
6
votes
4answers
447 views

How to apply a function to a list of tuples

trialList = {{0, 24.701}, {1, 24.69}, {2, 24.733}}; f[x_] := x + 1; I would like to apply the function f to only the second ...
2
votes
1answer
108 views

How to extract the bin width from a Histogram made with an automatic binning method?

I am using the Scott binning method with Histogram and Histogram3D to plot some data. How could I find out the bin width chosen ...
9
votes
4answers
246 views

How to pass a list of arguments into HoldAll

I have a list of arguments (which in reality is lengthy): arguments = {a, b, c} arguments2 = {a_, b_, c_} f[Sequence@@arguments2] := a + b + c Note: It seems ...
11
votes
5answers
309 views

Faster way to convert triangle list to edge list with no duplicates

I have a list of triangles returned by a Delaunay triangulator, in the following format: ...
6
votes
2answers
310 views

How to punch a hole in some 3D distribution of points

Suppose we have a long list of 3D Cartesian coordinates, defining a distribution of random points in 3D space. How could we remove all the points inside a sphere of radius ...
6
votes
1answer
129 views

Position with Except returns first item {0} and last item {}. Why?

Here is a simple list: l={1, 0, 2, 1, 0, 1, 0, 1, 2, 0, 2, 0, 1, 0, 1, 0, 0} To get the position of non-zero elements I use ...
7
votes
1answer
238 views

DeleteDuplicates[] does not work as expected on floating point values

Here is my simple example, and in this case function DeleteDuplicates does not work as expected. I want to FindRoot of my ...
5
votes
3answers
306 views

Replace very small numbers by zero in the output of a list

I have a long nested list, but many elements are numbers of order 10^-18 or less, eg ...
4
votes
1answer
136 views

Integrating a list of functions

For the purpose of this minimal example, let's say we have a list of functions, like this: f[y_?NumericQ] := {NIntegrate[z*y, {z, 0, 1}], a y} I want to ...
1
vote
1answer
152 views

Syntax for integrating over limits specified by a Table

I wish to use NIntegrate to compute multidimensional integrals. However, I don't want to manually input the limits for the dimensions. I want to store the ...
4
votes
2answers
147 views

How to only work on sublists with non-zero (or positive) values

i have a large compositional dataset which contains non-zero and zero values. here is a sample: ...
3
votes
7answers
254 views

Remove elements at certain positions from all sub-lists?

Consider a big list where all the inner lists length's are the same list = {{x1, y1, z1, t1}, {x2, y2, z2, t2}, {x3, y3, z3, t3}, ...}; elementNo = {4, 3, 2}; ...