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

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0
votes
2answers
98 views

How do I sum up p items in a sequence?

I have the following sequence list = {p1, p2, p3, p4 ....} I am summing up the p items as follows: p1 + p2 + 2*sqrt (p21*p2) = p12 p12 + p3 + 2*sqrt (p12*p3) = p123 p123 + p4 + 2*sqrt (p123*p4) = ...
0
votes
1answer
122 views

Matrix operations performed with column-vectors

We have 3 matrices: m1, m2 and b. We want to apply matrix operations (dot or sum) in a ...
6
votes
2answers
295 views

How can I create a class of matrices programmatically?

I am trying to figure out how to create a function that can create the matrix pattern below, where: f[1] returns {{1}} ...
1
vote
3answers
289 views

Defining a function as a sum of several Gaussians

I have a function that is a summation of several Gaussians. Working with a 1D Gaussian here, there are 3 variables for each Gaussian: A, ...
1
vote
1answer
72 views

Elements of a List according position in axis

({{a, b}, {c, d}}) a, b, c and d are Lists of 300 length. Their first 4 elements must specify their position in the column (1 column, 2 column, etc) and the ...
2
votes
2answers
119 views

Select words from different rows of column headings

I have a 2-dim array. The first 3 rows have column headings. The heading can be a single word, or 2 words (which take 2 rows) or 3 words (which take 3 rows). For each column I know which row has ...
1
vote
1answer
319 views

ListDensityPlot and ListPlot3D with big data [duplicate]

I have a large data set (512 x 512) and I have problems plotting it. ListPointPlot3D works fine But ListDensityPlot won't go through all the points (the same goes for ListPlot3D): Is there a way to ...
1
vote
1answer
106 views

Nest Replace Function with different rules

I have a table of data that I want to filter. Any value of zero in the table means that value was not calculated, so it should get populated with the tag "NC". Next the table is filtered for all ...
2
votes
2answers
121 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 ...
1
vote
1answer
89 views

Is this the expected behaviour from Partition when padding is inserted at the start of the list?

The documentation for Partition shows an example of partitioning without padding, so that no elements are dropped, but the last sublist can be shorter. ...
3
votes
2answers
125 views

Find Lists with intersecting sublists

I have a list of the following form: ...
1
vote
1answer
147 views

Check every list element for appearance

I'm used to MATLAB so this might be a stupid question but Mathematica is freaking me out. I have a big matrix with the following format: ...
0
votes
0answers
37 views

Grabbing columns from a matrix [duplicate]

If I have a matrix - exampleMatrix = {{A1,B1,C1},{A2,B2,C2},{A3,B3,C3}}; And I want to create a matrix like - ...
0
votes
5answers
99 views

Merge two lists for List3DPlot [duplicate]

I have a two lists: list1 = {{x1, y1}, {x2, y2}, {x3, y3}, {x4, y4}, {x5, y5}} and list2 = {z1, z2, z3, z4, z5} and I want to ...
3
votes
3answers
297 views

How can I extract multiple spans from a list?

I know in Mathematica, I can do A = Range[100]; B = A[[50 ;; 60]] B will then contain the 50th through 60th elements of A. Now, what if I wanted B to take 10th ...
2
votes
3answers
198 views

Using Part rather than Extract

In my work I found that I needed the Extract function. However I was wondering if there was a way to use Part. Assume that ...
1
vote
2answers
120 views

Clearing arguments passed to a Module

Is there a possible way to clear the arguments passed to a module to release some memory. I believe that arguments passed to modules are passed by value rather than pass by reference. e.g. I have the ...
4
votes
2answers
170 views

Replacing one element of list

I have a list of sequences of x's and y's. I want to switch the last position to the "opposite" symbol - if ...
12
votes
5answers
474 views

How would you efficiently implement BinListsBy?

Let's say I have a list like this: data = {{21, "Alice"}, {27, "Bob"}, {22, "Charles"}, {34, "Dora"}, {75, "Eliza"}} containing ages and names of persons. What I ...
5
votes
8answers
688 views

How to add a column to a table that counts the number of times the lines appear?

I am at a complete loss at this. I have a table with 2 columns and n lines. Some of the lines are repeated. What I want to do is add a new column that counts the number of repetitions of each line. ...
0
votes
2answers
652 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 ...
0
votes
1answer
122 views

Select duplicate values from a list [duplicate]

How can I select the duplicate values in a list? Example: {1, 2, 1, 1, 1, 1}
15
votes
6answers
1k views

Generating an Ulam spiral

An Ulam Spiral is quite an interesting construction, revealing unexpected features in the distribution of primes. Here is a related topic with one answer by Pinguin Dirk, who has provided one ...
6
votes
6answers
3k views

Convert a string into a list of numbers

I got the following problem I don't know how to solve or if it's at all possible to solve(I'm quite new to Mathematica and don't have an IT background, so please explain slowly if possible:)) I'm ...
0
votes
3answers
170 views

Trouble understanding a piece of code found on Wolfram Blog

I am trying to go through this Wolfram Blog example: http://blog.wolfram.com/2009/02/12/flag-analysis-with-mathematica/ on country flag analysis. I am having a problem understanding the following ...
1
vote
2answers
79 views

Replacing a specific pattern of values at level 2 in a list

I've a list of lists, tl = {{True, False, m12}, {False, m22, m33}, {m32, False, True}} and each nested list has the same length, What is the proper way to ...
4
votes
3answers
1k views

How to test if all the elements in a list are Integers? [closed]

Consider a list such as s={1,2,3,3,5,6,3} With IntegerQ[number] , you know if number is an ...
2
votes
2answers
559 views

Create a matrix of matrices using Band and ArrayFlatten [duplicate]

I can easily write a simple Band matrix using: SparseArray[{Band[{2, 1}] -> a}, {Dim, Dim}] where a is a number. Now, I ...
4
votes
2answers
279 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
4answers
291 views

Delete Missing data from coordinate sets

I have a list of pairs of coordinates, where some are missing. ...
3
votes
2answers
306 views

Permuting elements within a list

I have s = {2, 3, 5, 7, 1, 4, 6} (* always with diffente elements in {1,2....7}*) l = Length[s] n = 3 and n tells us that we ...
1
vote
1answer
63 views

Resolving Error: Mathematica evaluation order on Lists

I have a table that is 27 x 27, each entry corresponds to an element from the periodic table. I use the replacement rules in element list to allow me to convert a list of elements into a list of ...
2
votes
2answers
111 views

Importing Data and Devoting Their Names to Them

There are some files in a directory. I have used of SetDiroctory to access all of them. SetDirectory["C:\\Users\\SE7EN\\Desktop\\mathematica\\test"]; I can visit ...
10
votes
4answers
386 views

Complement of multisets

Given lists $a$ and $b$, which represent multisets, how can I compute the complement $a\setminus b$? I'd like to construct a function xunion that returns the ...
2
votes
1answer
62 views

Complement for a Matrix

In a matrix, there are some non-zero elements same as: aA= Also, there is a list such as: list = {a, b, c, d, e, f, g, ii, jj, kk}; I want to access to ...
2
votes
2answers
192 views

make a list based on two other lists

I have two lists: list1={4,6} list2={1,2} and I now want a function f that produces f[list1_,list2_]:={1,1,1,1,2,2,2,2,2,2} ...
1
vote
0answers
65 views

A more efficient way of fitting a non-linear model that returns an entire list?

I have a function that takes two parameters, del and nu, and returns a list npoints long ...
4
votes
3answers
405 views

Efficient matrix / array generation

What is the most efficient way of generating the following matrix? $\left( \begin{array}{ccccc} 1 & 0 & 1 & 0 & 1 & 0 & 1 & \dots\\ \frac{1}{2} & \frac{1}{2} & 0 ...
2
votes
1answer
248 views

how to apply a function to a list of tables

I have several files, and I want to extract for each of them a table, and then select just numbers, and keep only rows with five elements. My code works fine during import ...
2
votes
2answers
107 views

select from a list based on digits

I wish to know how do I count the number of occurrences of numbers that end in digits d. e.g. Say I create a list of Divisors of 12! I now want to count those divisors that end in 12. Like 12 & ...
0
votes
3answers
155 views
0
votes
2answers
164 views

How do I perform the riffle function backward? [duplicate]

I know riffle will combine the lists {1,2,3} and {a,b,c} to be {1,a,2,b,3,c}. Is there a way to work backward and split the list {a,b,c,d,e,f} to be {a,c,e} and {b,d,f}?
8
votes
2answers
438 views

Aligning two lists

I have two lists, L1 and L2, each with a key and some data. Let us say the key is a person's name, a string, and the data follows. (To respond to rasher's query:) Let us also assume the lists are ...
1
vote
2answers
480 views

position of element in a list using a function

How can I find in a list l the positions of all elements satisfying a boolean function f. For example, how can I pick in ...
3
votes
6answers
368 views

How can I construct a distance table?

I have a list of city names (of arbitrary length), f.e. c = {"BAL", "NYC", "LAS", "AUS"}; and the distances between them : ...
1
vote
2answers
414 views

Find equal elements on a list

Consider the following code to produce the sequence $x_1,\ldots,x_{n+1}$ where $x_i=11\cdots1$ ($i$ digits 1). Is there an easier way to do this? ...
2
votes
1answer
119 views
0
votes
1answer
85 views

Taking Mean for several elements of a list [duplicate]

i have the following question: Let us assume we have the following list: list={1.1,1.2,1.0,2.1,2.2,2,0,3.1,3.0,3.2} I need a function that always takes three ...
1
vote
3answers
252 views

Working with nested matrices

I have a matrix: A = {{a, b}, {c, d}} But each its element, itself, is another matrix too. ...
0
votes
1answer
168 views

How to load data into a Manipulate expression

I have data showing truncated octahedron geometry changing with time. How can I read those data into a Manipulate expression? To be specific, I want to manipulate ...