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

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3
votes
1answer
123 views

Sectional averages of a list

I am working in Mathematica. I have a table of 200 elements. I want to calculate the mean value for the first 20 elements, for the second 20 elements and so on, up to 200. I will get a table (matrix) ...
3
votes
1answer
559 views

Converting truth tables to boolean expressions

I have a truth table for a Boolean expression represented like this ...
3
votes
1answer
164 views

How to make a simple tree yourself with defined distances for each generation?

I'm trying to make a function that generates a tree for spin spin analysis in spectroscopy. I though it would be pretty easy, but I'm totally stocked. The tree should look something like this: ...
3
votes
1answer
3k views

Filtering Lists in Mathematica [duplicate]

Possible Duplicate: Select/Delete with Sublist elements? I need help in filtering long lists of x,y coordinates.Lets use the following list as an ...
3
votes
1answer
514 views

Removing an ordered pair from a list of ordered pairs if the second element in the list is Less than a Value

I have a list of ordered pairs from a piezoelectric sensor sampled at 2kH. The first element is time and the second, amplitude. I'm trying to remove all ordered pairs in the list of ordered pairs when ...
3
votes
2answers
579 views

hexList[[1]] returns a list of decimal numbers

Sorry for not being clear about this question earlier. I appreciate the answers I got, but the edits I made should make the question more understandable. I have been working with hex in ...
3
votes
1answer
165 views

splitting a list into files

Given is a list with x, y, z coordinates: {{100, 94, -1.112}, {100.05, 94, -1.112}, {100.1, 94, -0.982}, ..., {100, 94.25, -1.112}, {100.05, 94.25, -0.855}, {100.1, 94.25, -0.728}, ..., ...
3
votes
2answers
73 views

Manipulation of .csv imported data — no blanks in either of two lists

Above is a .csv file. I am trying to construct two lists of male and female math test scores such that only districts which include info for both male and female students are included i.e. neither ...
3
votes
3answers
97 views

Selecting sublists of different length if at least one element of the sublist fulfills a criterion

I have the following list, containing sublists with 1,2 or 3 elements. ...
3
votes
3answers
113 views

Change matrix elements at specific locations?

Let's say I have an array a={{1,2,3}, {4,5,6}, {7,8,9}} I want to have all elements along the diagonal multiplied by 2. ...
3
votes
1answer
142 views

linear combination of successive elements in a list

Say I have a list $E$ and want to build a list $F$ with the entries $F_j=E_j-2E_{j-1}+E_{j-2}$. I know that this happens to be achievable by iterating the function ...
3
votes
3answers
240 views

Use map on a different level

I have just started to get used to Mathematica's Map, Apply, and related functions, and I can't figure out how to do maps that require working "one level down". For example, I am currently trying to ...
3
votes
1answer
151 views

Function that returns the second argument of Reap

I'm trying to create a function that returns only the second argument of Reap. Here's my naive guess of how it would go : Reap2[x_]:= Flatten[Reap[x][[2]],1] ...
3
votes
3answers
176 views

How to detect outlier in data of an unknown function $f(x)$

Suppose I have an unknown function $f(x)$ that is monotonic, convex and nonlinear by definition. I somehow evaluated it at 1000 nonuniform $x$ points. By ploting these data, I found a very obvious ...
3
votes
1answer
178 views

Manipulating list of matrices

I have a list of around 100 matrices, that looks like this ...
3
votes
2answers
100 views

Is the MaximalBy function still used [closed]

On the mathematica reference website it gives examples using the MaximalBy function, However when I am using it, I see no desired output. This leads me to wonder if mathematica has stopped using this ...
3
votes
5answers
237 views

Take the next element in a nested list

My problem is the following: Consider a list of elements. To better understanding my following explanations, I would take this example: ...
3
votes
2answers
127 views

Converting unevaluated lists to strings

I have a list like l = {2 - 3, 12 - 4, Times, aab} I want to end up with {"2-3", "12-4", "Times", "aab"} I have tried ...
3
votes
3answers
295 views

How to insert elements of a list into list of lists?

I have two lists. E.g. ...
3
votes
1answer
191 views

Social Network Analysis - Get the End Points of an Edge

I want to get the end points of an Edge of a Graph. For example see the following source, ...
3
votes
2answers
277 views

Mapping multiple functions over an array

I am looking for an elegant way to Map multiple functions over an array. My problem looks something like this: Consider a list of functions: ...
3
votes
1answer
211 views

Extracting function calls from an expression

I have an expression like this: expr = F[0, 1] + 2 F[0, 0] - 17*F[2, 0] and I want to transform it to a list consisting of all function calls with its arguments: ...
3
votes
2answers
606 views

How to plot several functions without jumping? (multiple eigenvalues of a system as functions of 2 parameters)

I've been working on this research problem for months with some success by no global/proper solution to the problem. So I have square, Hermitian matrices of various sizes ($8,20,38$ dimensions) with ...
3
votes
6answers
331 views

Compute ratios of elements in two lists

I have two lists, say a and b, both of length n. I'd like to compute the following: ...
3
votes
1answer
72 views

Why does Thread FileDate give an error message?

I tried for example Thread[FileDate[FileNames["new*", "h:\\temp\\", 1]]] It gives FileDate::fstr: File specification ...
3
votes
3answers
97 views

Filling in explicit zeros in a (x,y) list for nonexisting y values for discrete Fourier transform in Mathematica

I have a list of (x,y) values in Mathematica for various discrete x values, as in ...
3
votes
3answers
192 views

Renaming a list with name obtained interactively

I have a list say: m = {1, 2, 3} The list is inside a package, and is the result of a calculation. I want to give the user the option to rename it, for example ...
3
votes
1answer
159 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}} ...
3
votes
1answer
247 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 ...
3
votes
2answers
1k views

Function returning Null along with other unexpected expressions

When I use some function, at the end along with the output I get some NULLs returned that I don't understand the reason for and are highly undesirable. For example, when I define the reversal of list ...
3
votes
1answer
279 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 ...
3
votes
1answer
211 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 ...
3
votes
1answer
253 views

Implementing Position

As an assignment I need to re-implement Position. I've managed to do this except for one small thing, the resulting list is not in the current format. The following ...
3
votes
2answers
57 views

Select elements from list with given head

I would like to select elements from list by specifying their head. E.g. SelectWithHead[{1,2,3.5,x}, Symbol] = {x} SelectWithHead[{1,2,3.5,x}, Real] = {3.5} What ...
3
votes
3answers
135 views

Finding largest Range in a list

In a list of positive integers, I would like to find the largest n such that Range[n] is a subset of the list. So for example ...
3
votes
4answers
133 views

How to Remove Undirected Edges that are the Same [duplicate]

Given: theData = {1 <-> 2, 2 <-> 3, 2 <-> 1} I would like to remove any duplicates where I define a duplicate to be: ...
3
votes
2answers
146 views

Convert matrix rows into variables

Can anyone show me how to set all matrix rows to variables. For example, I have matrix w={{1,2,3},{3,2,1},{0,0,0}} and I need to set each matrix row to be separate ...
3
votes
3answers
327 views

Faster Integer Approximation of pi

I'd like to speed up this calculation: First[Sort[Table[{k,Abs[Round[k/Pi]Pi - k]1.{k,1,100000}],#1[[2]]<#2[[2]] &]] The code above generates a list of ...
3
votes
2answers
100 views

Wrapping Interval Notation for Take

I'm trying to implement the solution to a math problem in Mathematica, but my code can't handle a particular boundary case. I think that I could implement a function that would do what I want it to, ...
3
votes
3answers
141 views

Elegant way for map a function over the columns of an array

I have an array data = {{1, 2, 3}, {4, 5, 6}, {7, 8, 9}}; And I want map Standardize over the column of the array. I use ...
3
votes
2answers
253 views

Dealing with a huge dataset

I have two ingredients here: a big dataset contained in a list, with ~ 20M values. a function that takes as each element of the list as input and yields True or False I want to save somewhere the ...
3
votes
1answer
265 views

Plotting with ColorFunction -> GrayLevel - no black

This is probably a fairly trivial question, yet I have been unable to find an answer - help would be much appreciated! :) I am trying to plot a 28 x 28 matrix (tabulated data given here), containing ...
3
votes
3answers
93 views

How to get different items in a list to interact to get a result?

I have two lists, for example (the real lists are much longer): list1 = {1, 2, 3, 4, 5, 6, 7}; list2 = {9, 10, 11, 12, 13, 14, 15}; I want to create a single ...
3
votes
2answers
199 views

Variable length list with # and [[i]] as elements

I need to create a list that as an input receives the number $N$ of elements that it will contain and that returns: ...
3
votes
1answer
147 views

How can I get a single solution to a set of inequality constraints?

I have a set of constraints to which I require integer solutions. However, instead of needing all possible integer solutions (as obtained by using ...
3
votes
2answers
279 views

Listable compiled function using Map

I'm trying to minimize the computation time of problem which is too long to post. I use compilein order to gain some speed. To increase speed I would like to use ...
3
votes
2answers
552 views

Mathematica: summing over n abstract indices

This probably has a one line answer, but I'm totally stuck. I have two tensors, i.e. two objects that depend on NN abstract indices which i've labelled ...
3
votes
2answers
97 views

How to uncompress only the compressed elements in a matrix

I have data in a rectangular structure – something like matrix={{a,b,c},{d,e,f},{g,h,i}}. The problem is that some of the columns consist of uncompressed data and ...
3
votes
1answer
320 views

Formatting data tables with Grid + Dividers vs. SplitBy --> GridBy?

A quick method to format human-readable data tables with headers, is to use Grid, eg: ...
3
votes
1answer
221 views

Exchange axes in ListLinePlot

I'm sorry to do this right off the bat, but I have the following set of data: ...