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

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3
votes
2answers
69 views

Retaining relative sizes of local maxima using MaxDetect[List]

I would like to be able to find the position of the two greatest local maxima in a list. For the example: list={1,2,3,4,2,1,2,6,5,4,3,2,} I would like to return ...
4
votes
3answers
70 views

Replace values in a list based on conditions

I have a list with negative and positive numbers list = {-1, -2, 1, 2} and I want to replace all negative values with 0 and all positive values with 1 ...
3
votes
1answer
129 views

Programming for matrix manipulation

I want to write a programme which operates on nd x nd matrices. The programme looks the matrix as a n x n block matrix where ...
19
votes
3answers
3k views

Data interpolation and ListContourPlot

I am fairly new to Mathematica and I have two quick questions on using it for a Hydrology and Hydrogeology class. One is about data interpolation and interpolating without any data defined in an area. ...
6
votes
5answers
319 views
2
votes
1answer
64 views

How do I define a random variable involving Part?

I need to define a random variable that involves Part, but when I try, for example ...
16
votes
10answers
689 views

Count the sequences in an array

Is there a short and easier way to count number of sequences in a list? Let's say I have three lists: list1 = {0,0,0,0,0,0,0,1,1,1,1,1,0,0,0,0,0,0,0} ...
1
vote
2answers
72 views

Formatting a table of values

How do I display a list of values $\{a_1,a_2,\ldots,a_n\}$ in a two column format? --------- 1 | a_1 2 | a_2 3 | a_3 ...... n | a_n I tried ...
2
votes
2answers
38 views

Join data imported in different variables [closed]

I've imported data from Excel into several variables and I would like to join all data in one "big" variable. I seem to have a problem when one variable contains numerical data... ...
1
vote
2answers
83 views

Ask about the variable and constants in partial derivative in a loop

EDITED I have a function in a list like : func={2(x^2)+x*y+3(y^2)}; I want to have a UI that ask me which parameter (x or y) is a variable in a ...
0
votes
1answer
27 views

Transpose four lists of data into two lists for use in List Plot [closed]

I have four lists of data x1 = {1,3,5,7} y1 = {0,2,4,6} x2 = {10,12,14,16} y2 = {8,10,12,14} In one line is it possible to use transpose to get two lists which ...
2
votes
1answer
516 views

How do I sort complex numbers?

Okay, so I posted something about sorting, and it was linked as a duplicate to This post However, I am having problems trying to sort a list that contains both real and complex numbers. I put them ...
4
votes
3answers
130 views

How to get multiplication of the elements of a specific list/Matrix

Assume there is a list: List1={a,b,c,d}; Then I want to get these calculation: ...
3
votes
1answer
109 views

Map an Argument to a list of functions

I want to "map" an argument to a list of functions. Here is the concrete Problem. I generate a list "Messungfit" of functions: ...
0
votes
0answers
54 views

Switching ArcTan argument from a sequence to a list

The objective is to determine the angle formed by the line connecting two points in the plane, say p and q. The ...
0
votes
2answers
32 views

How to get Complement function working in a For loop? [closed]

I've been working on a piece of code that will delete small components from a nested uneven matrix (n pages, n rows, 3 columns), by deleting the pages with less than ~30 rows. However, I've notice ...
4
votes
2answers
114 views

Initializing several values of a function

How do I initialize several values of a function at once? Consider the function f[0] := 1; f[1] := 2; f[2] := 3; f[n_] := f[n] = f[n-1] + f[n-2] + f[n-3]; Is ...
2
votes
4answers
164 views

Given a matrix of integer, create a matrix with 1 or 0 according to which numbers are in the first matrix

Not sure the title gives the idea of what I need, so here is a sample: I have ten (w) combinations (subsets) of 20 (n) numbers taken 4 (k) at time. I need a matrix of dimension w x n with 0/1 in each ...
0
votes
2answers
72 views

Write list of numbers to a file

I have a list of numbers: e.g. list={1,2,3,4,5} To write the list to a file I use (here each integer number occupies 7 spaces): ...
2
votes
2answers
135 views

Approximation of definite integral by parabolas

This question is related to Trapezoid approximation to definite integral. As promised, I am now asking about how to draw approximation of integrals by parabolas. I tried to modify MarcoB's code, and I ...
7
votes
4answers
197 views

How to Apply Functions to Lists with Many Curly Brackets?

For example, consider the list defined below. samplelist = {{{1,2,3,4}}, {{5,6,7,8}}}; How would I apply the Times operator ...
2
votes
2answers
97 views

How to remove multiplicities from for a list in way meeting special criteria

I have a list of pairs, tabul, which has the property that the second element of each pair is also an element in my list data. I ...
0
votes
1answer
73 views

Elements inside arrays seem to be strings rather than signed numbers

When I have code like b = Array[Subscript[be, #] &, {3, 1}] b = b /. {Subscript[be, k_] :> Subscript[-be, k] /; k > 1} I am noticing that Mathematica ...
3
votes
1answer
138 views

Union of two or more lists

I have a number of lists (only 3 shown here) ...
0
votes
0answers
29 views

FoldList[Union,…] version 8 vs version 9 [duplicate]

I have a list of matrices something like shown below A = {{{1,1,1,1,1},{2,2,2,2,2}},{{3,3,3,3,3},{4,4,4,4,4},{5,5,5,5,5}}} When I try to run the code ...
2
votes
2answers
115 views

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

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 ...
0
votes
2answers
315 views

Extract X value from corresponding Y value from a List or Transpose [duplicate]

I have a list of X values and Y values separately, and also together with: data=Transpose[{X,Y}] This data is from a chromatogram, and I want to extract the ...
2
votes
2answers
95 views

How can I get a certain kind of iteration?

Can I get this type of do-loop in Mathematica? Do[Print[j," ",k," ",l], {j,k,l, {a, b,z}, { c, d,y} }] I want this to work so that, in the first iteration, ...
3
votes
1answer
57 views

Iteration variable in variable [duplicate]

Is it possible to create following list by some sort of iteration? {a1,a2,a3,...,a100} I cannot think of any way to append a to ...
2
votes
3answers
101 views

Efficient extraction of a subset

The context is molecular dynamics. The data is in the format (index_1, index_2, distance). The goal is to find all of the distances to the neighbors of point index_0 and to present a set listing the ...
0
votes
1answer
424 views

Generating all “from n choose k” configurations of a simple list [duplicate]

Suppose that I have a 1-D list called myList. Here's an example: myList = {"A", "B", "C", "D"}; I want to write (or find ...
1
vote
1answer
52 views

How to set the values into some variables from different lists [duplicate]

I have a list of Values and a list of variables. I want to set the Values into Variables. Assume the following code: ...
1
vote
0answers
40 views

Generate a list of values of a function for each value of the parameters already found

The following question is an extension of this question Find all roots of a function with parabolic cylinder functions in a range of the variable. Now I want to use the roots found to calculate a ...
7
votes
1answer
128 views

Automatically grouping words into categories

Say I have a comma-separated list of words. For example sake, let it be things I have seen during my trip to a safari zone. It would look something like that: ...
1
vote
2answers
133 views

Query in Lists Mathematica - Pivot table

Recently, I finished a simulation, and I got the following data: ...
1
vote
0answers
53 views

How to remove brackets from this list? [closed]

I have some lists which have many brackets. I'd like to remove brackets from the lists. For example, I need to change the list ...
6
votes
3answers
197 views

Merging lists of pairs [duplicate]

I want to add several fluorescence spectra. They are lists of the format ...
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 ...
3
votes
5answers
133 views

How to filter list of list of rules on certain condition?

For example, Solve[] returns all solutions as a list of list of rules. And mine looks something like this: ...
10
votes
3answers
358 views

Modifying strings in a list efficiently

I have a list of strings $\{s_1,s_2,\ldots,s_n\}$. I would like to to produce the following list of strings: $$ \{s_1<>1,\ 1<>s_2<>1,\ldots,\ 1<>s_n\} $$ In other words, I want ...
10
votes
3answers
368 views

Riffle and Partition

At some point I noticed that I was using Riffle and Partition together a lot. I would do things like ...
18
votes
9answers
2k views

Selecting a sublist based on Length

If you have a simple list of lists as follows: test = {{1, 2}, {4, 5, 6, 7}, {5, 4, 3}} How do you ask Mathematica to return the sublist of greatest length? ...
5
votes
4answers
161 views

Create Nested List from tabular data

Im trying to create a nested list from tabular data, then onward into a nested association. I can get part way with the help of this answer but it only works for the first level. Repeated use of this ...
18
votes
7answers
8k views

Mathematica: finding min/max in list

I have a list of coordinates like this one: {{x1,y1},{x2,y2},{x3,y3},...,{xn,yn}} I need to get the minimum and the maximum of all x-values and the minimum and ...
3
votes
0answers
77 views

speed up evaluating a listable function

I apologize in advance for the vagueness, but I can't think of a more descriptive title. I am trying to find the average value of the square of BesselJ[0, x] ...
13
votes
4answers
353 views

I have the minimum Y value. I want to find the corresponding X value from the list [duplicate]

I have a very big file and contains data in the format of {x,y}. I got the minimum Y value by using data[[All, 2]] // Min[#] & Now I want to get the X value ...