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

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0
votes
2answers
146 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, ...
2
votes
1answer
273 views

Deleting selected rows from data table [closed]

I'm an intermediate Mathematica user and the select function presented on Data Table Manipulation in Mathematica: Step 2 was very useful in helping me manipulate a 36Mb data file - 13 columns and 180k ...
1
vote
1answer
58 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
103 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
94 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
104 views

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

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
81 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
111 views

Find Lists with intersecting sublists

I have a list of the following form: ...
1
vote
1answer
135 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
33 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
86 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
237 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
185 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
105 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
153 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 ...
11
votes
5answers
447 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
490 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
256 views

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

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
90 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}
8
votes
5answers
959 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
2k 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
167 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
74 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
399 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 ...
3
votes
2answers
254 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
225 views

Delete Missing data from coordinate sets

I have a list of pairs of coordinates, where some are missing. ...
2
votes
2answers
215 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 ...
0
votes
1answer
49 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
99 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 ...
8
votes
4answers
325 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
52 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
183 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
49 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
390 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 ...
0
votes
1answer
132 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
99 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
2answers
143 views

Improving code for comparing and modifying nested matrices

I have a matrix such as: ...
0
votes
2answers
118 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
374 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
281 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
336 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
279 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
109 views

How to find all possible correlations between n vectors

Given the Matrix ...
0
votes
1answer
64 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
172 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
162 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 ...
0
votes
1answer
45 views

Testing a certain function over multiple levels

I regularly want to test if a certain function, here foo, gives the expected result when mapping it over n - level - matrices. My naive approach is to write: ...
0
votes
1answer
94 views

Swapping rows and columns in matrix [closed]

If I have an array like the following $\left( \begin{array}{ccc} 1 & 2 & 3 \\ 4 & 5 & 6 \\ 7 & 8 & 9 \end{array} \right)$ How can I swap the rows and columns, so it is ...
0
votes
2answers
786 views

How to pass a list as function argument?

I have the following function lFreqPhylo[a_, Q_, b_, p_] := Sum[Log[freqFunction[r[[p]][[i]], L[[p]][[i]], a, Q, b, {i, 1, nbranches[[p]]}]; The objects L, r ...
0
votes
0answers
34 views

Unexpected results from Thread [duplicate]

I've run into an issue where threading two lists with a generic function, f: Thread[f[{{1,1}, {2, 2}, {3, 3}}, {4, 5, 6}]] ...