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

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1
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6answers
212 views

Deleting missing data with CountryData

I need to delete all of the missing entries after executing this line: ...
1
vote
3answers
190 views

How to manage list of list of rules?

Considering we have a list: str = "{1 -> {a -> aa, b -> bb}, 2 -> {2a -> \"{b -> bb}\"}}" Bringing this to expression gives: ...
0
votes
0answers
55 views

How to handle substrings of a matrix by a named index

I am using open source code to run stochastic simulations. The output looks like this: ...
2
votes
3answers
111 views

Max function used with nested lists

I have a list as follows lis1={{{1,5,6},{4,7,8}},{{1,2,2},{5,6,7}}} and would like to calculate the max value of each nested list in order to get following ...
1
vote
0answers
31 views

Tracking solutions over a Brillouin zone

Thanks to @bbgodfrey I have a function that finds the two solutions to a set of equations bounded by a hexagonal region (corresponding to the Brillouin zone). It takes the angle ...
18
votes
4answers
402 views

Make MapIndexed listable

My goal is to apply MapIndexed to every element of a nested list without destroying the arithmetic operations within the elements. For example, let's start with ...
2
votes
4answers
91 views

Pairs of data to Classify[]

Suppose I had the following data a={1,2,3,4,5} How would I turn this into b={{1,2,3}->4,{2,3,4}->5} That is, ...
4
votes
2answers
100 views

Output function control and manipulation for efficient computation [closed]

I have taken note of a similar post related to modifying function parameters. I tried to adapt Kuba's solution to this post but I can't get it to work. I will illustrate my problem using a similar ...
0
votes
1answer
58 views

How can I use nonlinear model fit with multiple variables? [closed]

I have a data set with four entries. the first three entries correspond to variables in the fit x,y, & z. The fourth entry corresponds to the function value. I am trying to fit this data to a rate ...
8
votes
1answer
120 views

ListConvolve Memory Hemorrhage

I wrote a routine that convolves an impulse response array with a test array and checks for the RMS difference between that convolution and a data array. I do this iteratively so that I can modify the ...
3
votes
0answers
150 views

FindPeaks finds Minima, but not all of them [closed]

I have 10 sets of data, which are the result of measuring the way of a mass falling down over time, bringing a wheel into rotation when the mass hits the ground and then the wheel lifts the mass up ...
24
votes
4answers
4k views

K-means clustering

In MATLAB, there is a command kmeans() that divides an array into $k$ clusters and calculates the centroid of each cluster. Is there any command in Mathematica to ...
0
votes
0answers
66 views

Matrix iteration failing after second step

I am calculating 11x6 matrix using different logics as in below code. Problem is in Do loop in below code where I have two different criteria to update matrix "fd". I am expecting logic in IF which ...
0
votes
4answers
95 views

How to trim the zeros from the right of a list? [duplicate]

I need to remove the zeros from the right of an integer list up to the first non-zero element. Such as {0,1,0,0,2,0,0}->{0,1,0,0,2}. Padding zeros can be simply ...
5
votes
6answers
588 views

Can Mathematica delete some of the 0's from a list?

I have a list: {1,2,3,0,0,4,5,0,0,0}. I want to delete the 0's occurring after the last positive integer. In other words, I ...
0
votes
1answer
54 views

How to import data from a .mat or a .txt file and manipulate dimensions

I'm new to Mathematica (I know very, very little - so I apologize if anything I say is absolutely wrong) - but I'm trying to upload a file from matlab and arrange it in matrix form. I have a .mat ...
31
votes
5answers
2k views

How to efficiently find positions of duplicates?

Is there an efficient way to find the positions of the duplicates in a list? I would like the positions grouped according to duplicated elements. For instance, given ...
19
votes
5answers
1k views

Moving maximum function?

How can I construct a moving maximum function? For example, if I have a list of 12 values: { 5, 6, 9, 3, 2, 6, 7, 8, 1, 1, 4, 7 } and I want to maximize over 3 ...
1
vote
1answer
30 views
0
votes
1answer
49 views

Replace element of matrix based on rule which invloves other element of same matrix

I am trying to replace 1s row of matrix d iteratively from right by multiplying last element in 1st row with (1-int*dt) to generate 2nd last element. The replacement continues till I reach the 1st ...
1
vote
2answers
118 views

How can I reshape my solutions to make a 3D plot?

I need some help on the following. I need to run Solve for multiple values of a and b. To do so instead of using Do, I use ...
3
votes
2answers
119 views

Dynamic arrays and lists with compile (Append, Linked lists etc.)

I have a code that I need to compile. The code contains a loop in which I need to gather data into a list. The question is how to best gather data so that the code works inside Compile. The following ...
3
votes
1answer
190 views

How can i subtract a surface from another

I have one surface which i got with using analytical solution. And one by ListPlot3D. My question is how can be withdrawn from the one from the another. ...
1
vote
1answer
33 views

Replace parts of nested lists

I have list of stock data as follows: lis1= {{{1992/10/12, 126.946, ^AEX}, {1992/10/13, 127.85,^AEX}}, {{1992/10/12, 88.487, ^AFLI},{1992/10/13, 91.825,^AFLI}}} ...
0
votes
0answers
54 views

How to replace a part of array based on certain rules which involves usage of other array

I am trying to replace outermost column of array "fd" in below code. fd is matrix of dimension (nas1,nts) which is initially filled with 1. I want to replace outermost column of fd with result of Max ...
1
vote
3answers
89 views

2D Interpolation of data file

I hae a datafile with 5 columns of the structure: x_i f(x_i,y_1) f(x_i,y_2) f(x_i,y_3) f(x_i,y_3) f(x_i,y_4) with i = 1 to about 100. Thus there are about ...
6
votes
3answers
231 views

List and patterns

Given some tuple $\{N,M,L\}$ such that $N\geq M\geq L\geq 0$ and $N>0$, how can I generate all tuples $\{n,m,l\}$ such that $n\geq m\geq l\geq 0$ and such that ...
4
votes
1answer
94 views

Better method to swap the values of two 2-D arrays

I have two 2-D matrices $A$ and $B$(owns same dimentions) which have the style written as below: $ \begin{bmatrix} a_{11} & a_{12} & \cdots & a_{1k} &\cdots &\cdots & ...
13
votes
1answer
161 views

Unexpected slowness checking for empty list?

I thought I had a firm understanding of the differences between Equal and SameQ, but this has me puzzled: ...
1
vote
3answers
94 views

Finding roots of transcendental equation and collecting into a list

I am working on a physics reserach project for school and I have run into some troubles working Mathematica. I am a fairly inexperienced mathematica user so any help would very much be appreciated. I ...
0
votes
0answers
24 views

NCAlgebra to calculate a Hermitian conjugate

I have to calculate a non-commutative product of this form: $(-H a+ J a b)**(-H a + K c)$ where $H,J,K$ are variables and $a,b,c$ are operators that don't commute. For this purpose I used the package ...
2
votes
3answers
94 views

Shorthand to write repetitive test in mathematica

I have the following set of Mathematica statements: ...
2
votes
3answers
66 views

Flattening of Matrix rows [duplicate]

It's got to be easy, but I can't come up with a general solution. m = {{16, 2, 3, 13}, {{5, 11, 10, 8}, {9, 7, 6, 12}}, {4, 14, 15, 1}}; What I'm trying to ...
0
votes
1answer
40 views

How to switch keys in a Map to Association [closed]

I have an association that has parameters for a function. These parameters represent two cases that need to be applied to the function. Some parameter values are common to both cases but some are ...
0
votes
0answers
30 views

How to generate the list of consecutive pairs from a list? [duplicate]

What is the morally right solution to mapping a list {a,b,c,...} to the list of pairs {{a,b},{b,c},{c,..},..}? The solution I came up with feels a little clumsy: Shift a copied list by one and form ...
-1
votes
1answer
57 views

Manipulate excel file and plot

I have a number of .csv files that have the following format: I want to do the following: ignore the last two rows sort all the remaining rows w.r.t the 2nd ...
21
votes
3answers
807 views

DeleteDuplicatesBy is not performing as I'd hoped. Am I missing something?

Déjà vu: a new-in-v10 function should provide a better solution to an old problem, but my enthusiasm is curbed when I run timings. This time the function is ...
0
votes
1answer
70 views

Unexpected results from output with NumberForm and ScientificForm

I wrote this little function to help me export tables with formatted numbers to files: (By the way, if you have suggestions on how to make it more efficient and compact, it would be great) ...
14
votes
6answers
708 views

Finding the period of an array of integers

A simple array of integers is given. The problem is to detect if a pattern is repeatedly occurring in the array, and find the length of that pattern. For example, for ...
3
votes
2answers
67 views

How to re-arrange lists, divide one list into 2 lists with a particular step [duplicate]

How to re-arrange following list: {a1,b1,a2,b2,a3,b3,a4,b4} or this {a1,b1},{a2,b2},{a3,b3},{a4,b4} to get: ...
1
vote
1answer
48 views

Collecting specific Lists of data in coordinate form

Note: This might be trivial for many of the users but i am new to mathematica so i don't know!!! Question: Suppose i have three list of data as follows: ...
37
votes
6answers
2k views

Find zero crossing in a list

I'm looking for a function that finds the index of the zero-crossing points of a list. Before I go making my own subroutine to do this, I was wondering if anyone knows of any built-in Mathematica ...
23
votes
3answers
394 views

Bug in MovingMap (breaking change between version 10.1 and 10.0.2)?

The MovingMap window spec has been changed between version 10.1 and 10.0.2. Version 10.0.2 ...
1
vote
2answers
51 views

Perform operation on part of a table / create a reference

There is a function f that I would like to operate on a rectangular part of a table t. The part is specified by function ...
0
votes
0answers
25 views

Generating a list consisting of function values like in a triangular matrix

A goal is to generate a SymmetrizedArray of dimension n^k with specified symmetry (let it to be ...
9
votes
5answers
373 views

Most efficient way of making pair list from a list

I have a bunch of datasets which looks like: 3 7 1 6 5 8 2 4 1 2 8 1 5 2 5 ... and I need to make a list of pairs such that the first element makes a pair with ...
2
votes
2answers
166 views

Are there any good mass row/column swapping functions for matrices?

I have the following matrix Keeping the 20 row and 20 column fixed (so the 21st rows and columns because I started at 0)...how do I push each row and column back one spot? I need to push the 0th row ...