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

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2
votes
2answers
1k views

Importing several huge files with headers & footers

having here several files in ASCII format http://ge.tt/91rv0Jf/v/0 I want to import, while removing headers and footers and then join the several lists. ...
5
votes
4answers
496 views

Any rule of thumb for converting a simple mathematical expression into a pure function?

By simple mathematical expression I mean one with a few functions and few variables copied into MMA in a mechanical way from a math book. For example this one, giving the distance between two points ...
1
vote
1answer
162 views

Splitting list of sums into a sum of lists

I want to split a list of sums into a sum of lists For example, I'd like to turn {{x + y + z}, {x}, {y}, {z}} into ...
5
votes
1answer
292 views

Is there an equivalent of “shiftdim” of MATLAB?

Recently I'm spending my time implementing some computer vision algorithms, which usually handle a large amount of data. The problem I'm facing now is that I have to reform my video data to pass it ...
6
votes
3answers
837 views

Replace “,” in a list with “.”

I have a list which consists of numbers which use comma (,) instead of dot (.) as their decimal point. I would like to replace the commas, but only those commas which are followed by more than five ...
1
vote
1answer
281 views

Partial row reduction of a matrix

I have an $m\times n$ matrix (presumably of full rank) with $m>n$, and I would like to row reduce it, but leave the last column unreduced; that is, I want to get output on the form $\pmatrix{ 1 ...
0
votes
2answers
167 views

Convert *.txt file

I would like to Import and Convert a *.txt file which looks like: https://docs.google.com/file/d/0Bw-308nJcF01Yl92RURCLUg4VzQ/edit?usp=sharing and turn it into a Matrix which I can use to make ...
24
votes
4answers
6k views

Finding Local Minima / Maxima in Noisy Data

I'm trying to find local minima / maxima in noisy data, consisting of data values taken at certain time intervals. Ideally, the function should take a pair of lists (one containing time values and one ...
1
vote
3answers
193 views

How can I create a new tables out of a table and plot it

I have the following problem. I have a table, call it m, which is labelled by 3 indices (say i,j,k), each of them running from 1 up to 100. I would like to be able to construct a new table which would ...
5
votes
1answer
555 views

nested use of Apply/Map/MapThread in pure functions

1. My main question I have a function with two argument slots. I wan't to apply this function to 2 lists with different length's. I thought in this solution: ...
5
votes
5answers
2k views

How to sum over a List

list = {11.5575, 11.397, 5.52734, 4.0878, 2.54815, 1.86652, 2.55028, 2.14952, 1.6242, 1.34117} I have a list of numbers. How do I make a function that creates a ...
1
vote
1answer
172 views

ReplacePart inside For loop

I am trying to replace the last column of the following expression (mat) by doing ...
2
votes
1answer
157 views

Plot several lines with different starting points on the x-axis

First of all, I would like to apologize in advance if I don't use the correct terms or if I express myself unclear but I just started to work with Mathematica. I'm simulating electricity prices and ...
17
votes
7answers
2k views

Find continuous sequences inside a list

I have a list which is something like this: {3,4,5,6,7,10,11,12,15,16,17,19,20,21,22,23,24,42,43,44,45,46} What I'd like to to is get the intervals which are in ...
0
votes
1answer
623 views

Keeping axes fixed in an Animate of a 3D graphic

I am using the following code to animate a 20 3D ListPointPlots: ...
6
votes
2answers
362 views

How can I find if the number of subsets for a list is very large?

I'm trying to find the following; Subsets[Range[2, 2300], {4}] but my computer gave the following error: ...
29
votes
1answer
561 views

How can I make threading more flexible?

Threading automatically with Listable functions requires the argument expressions to have the same length (or for one of them to be atomic). For nested lists the ...
3
votes
3answers
246 views

Logical AND operation over several comparisons

Let x and y be arrays defined as Array[x, m], Array[y,n] respectively. How to generate the following function of $x$ and $y$ for variable $k$: ...
3
votes
1answer
291 views

Including two ListLinePlots in a 3D graphic

I have two lists of data which I am plotting on two ListLinePlots. I would like to have these two plots appear perpendicular to each other on a 3D graphic. I have ...
-4
votes
4answers
173 views

Extracting the integers from a list

I have a list where the elements are Reals and Integers. How can I extract the Integer? For example, if I have {1, 2, 3.4, 9.9}, how can I get ...
1
vote
4answers
429 views

Summation over 3 lists

I have three lists. As an example, a = {10, 5, 6, 8, 7}; b = {4, 8, 9, 7, 9}; c = {7, 5, 12, 4, 1}; I want to get: $$ x(i)=\sum ...
0
votes
0answers
29 views

Error in extracting a column [duplicate]

I imported excel data to Mathematica using this command. kuruzD = Import[ "C:\\Users\\TMH\\Documents\\Problem Set 4\\kuruzData.xlsx"][[1]] //TableForm I want to ...
1
vote
3answers
401 views

How to find intersection of multiple lists excluding empty ones?

I have lists like list1={1, 1, 2, 3}; list2={3, 1, 4}; list3={}; I want to find the intersection of all list. I tried the following way, but it's not working. ...
1
vote
2answers
239 views

What ways are there to convert an Integer to a list of digits?

How can I convert an Integer to list of numbers? For example: 781049 ==> {7, 8, 1, 0, 4, 9} What are the possible ways of ...
2
votes
2answers
268 views

Efficient code for building a big list

I would like replace the following code ...
0
votes
1answer
346 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
376 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
55 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
379 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
6answers
2k 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 ...
15
votes
6answers
714 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 ...
2
votes
3answers
206 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
265 views

Better method for creating a tuple out of two lists

I just combined two lists using this method ...
1
vote
2answers
83 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 ...
2
votes
2answers
321 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
770 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
208 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
265 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 ...
19
votes
4answers
798 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
183 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
184 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 ...
11
votes
3answers
576 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
143 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
131 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
396 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
215 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 ...
-5
votes
5answers
560 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
808 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. ...
5
votes
1answer
187 views

Why is Flattening a CoefficientArray so slow?

I have a vector of $n$ degree $n$ polynomials in $(x,y,z)$, each of whose coefficients is an inhomogenous linear expression in $3 n^2$ variables. I want to write down the linear equations in these $3 ...
0
votes
2answers
156 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: ...