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

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5
votes
2answers
180 views

Create a list of rules built from data set fields

I want to convert a dataset to a list of features and a list of target values, for use in Predict and also more generally. I know ...
0
votes
1answer
35 views

Strange behaviour of Append [closed]

I have the following situation and I completely do not understand why the second system can be solved but the first (of the same equations, as it seems) cannot. How is it possible? ...
0
votes
4answers
114 views

Make a program that does union of two lists

I have to make a program that gives as a result the union of two lists using a For loop. I can't figure out how to inspect if the elements of a list are different. ...
2
votes
1answer
58 views

sparse array with list [closed]

i'm trying to populate a sparse array with lists in certain positions, i tried the following code, ...
4
votes
3answers
128 views

How to map over inner keys of nested Associations?

Considering an association: <|"a" -> <|aa-> "asc", bb-> "asd", cc-> 0, ImageType -> "asd", dd-> "asd"|>|> How can I make the inner ...
4
votes
4answers
705 views

Writing a circular matrix

I have two square matrices, $A$ and $B$, of the same size, say, of $m \times m$. What I want is to write a programme/function of three variables, $A$, $B$ and $n$, that outputs the $mn \times mn$ ...
1
vote
2answers
52 views

How can I manipulate this list?

I performed a loop with Table where I solve a system of 4 equations that depends on two parameters: eta and p. I create two lists for each parameter as follows: ...
2
votes
4answers
209 views

How to switch from array to string?

Considering we have an array: a = {2/3, 4/5, 9/7, 3/7, 1/7, 1/9}; How can I get this to be: "2/3 4/5 9/7 3/7 1/7 1/9" ...
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 ...
4
votes
4answers
113 views

Creating a new list from other two lists using for loops

I have two lists 'ups' and 'downs' where they are composed of positions of an element in a matrix and their weight. For example, ...
4
votes
4answers
190 views

How to highlight the elements in a list that match a pattern?

For example, {{1,2,3},{1,2,3,1,2,3,4,5}}with pattern {1,_,3}is transformed to ...
0
votes
3answers
53 views
1
vote
3answers
53 views

Delete permutations of subtables in a table [closed]

I've got a table of tables: $A=\{\{a,b\},\{b,a\},...,\{a,b,c,d,e\},\{e,d,c,a,b\},...\}$. How do I do to remove backward duplicates, or more generally permutations of duplicates in the table? For ...
0
votes
1answer
38 views

Create a Table depending of two variables [closed]

I tried to create a table depending of two variables as: W= Table[{G[[i]], G[[j]]}, {i, 1, 3}, {j, 1, 3}] I wanted it to look like ...
6
votes
3answers
96 views

Comparing elements of a set and deleting elements based on a criterion

I have a function that has two inputs. The first input is a set of 2-element sets, and the second input is a single 2-element set. My function complements each 2-element set with the second ...
0
votes
0answers
39 views

Procedure argument value change [duplicate]

I'm trying to create my own hamiltonian cycle algorithm using Mathematica for school, and I'm stuck on a syntax issue. I get the following error: ...
3
votes
4answers
218 views

How to switch from List of rules to Association?

Considering we have a list of rules: ...
8
votes
1answer
118 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 ...
0
votes
2answers
62 views

Writing a function with variable arguments [duplicate]

I want to write a function which takes multiple arguments varying from 1 to n, where each argument is a triplet. sublistProduct[{$a_1,b_1,c_1$},{$a_2,b_2,c_2$},...] = { $\Pi_{i=1}^{i=n}a_i ...
1
vote
2answers
62 views

How to make function accept list of rules as an argument?

Considering the list of rules: r= {"a" -> "1", "b" -> "2", "c" -> 3, d -> 231, "e" -> 1.25}; I want to have a function ...
2
votes
3answers
106 views

DeleteDuplicates in a list of 2-tuples under condition

Having a list of 2-tuples, I would like to delete such 2-tuples that have 0 at second position, but only those, whose first element is not unique in the list. E.g. ...
1
vote
3answers
189 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: ...
4
votes
1answer
69 views

Automatically assign Variablenames to multiple checkboxes

I want to implement the option to import data from Excel and then the ability to trim this data in order to fit the needs. The import from Excel: (source) ...
2
votes
5answers
79 views

Find list item before first negative value [closed]

If I have a list like this: ...
6
votes
4answers
302 views

How to delete Missing[“NotAvailable”] from list of rules? [duplicate]

Considering we have a list of rules: ...
1
vote
1answer
93 views

Accumulating elements of lists taking the criteria out of another list

In order to find the critical values for the significance of a discrete distribution, for example BinomialDistribution[20,0.6], i need a function which works on the ...
1
vote
0answers
39 views

Combine nested list entries [closed]

I have a list with stock index data (which I load from a database) as follows: ...
5
votes
3answers
217 views

Count elements of a list

Let's create a random list n = 100; data = Table[{RandomReal[{0, 2}], RandomReal[{-1, 1}]}, {i, 0, n}] Now we divide the $(x,y)$ plane into four sectors with the ...
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. ...
0
votes
1answer
122 views

Manipulating list based on Euclidean distance

I have an array of 101 matrices. Each matrix contains information like id, position (x,y,z), time etc about a collection of particles, looks like this ...
1
vote
1answer
92 views

Summing terms in Table

I have a table that looks like Table[m, {k, 10}, {j, k}, {i, j}] where, m is a square matrix that depends on the indices $i, ...
1
vote
2answers
76 views

Circular Playing up in a Grid

As we know, there is a possibility to emphasize some elements of a Grid by highlighting its cell with ...
8
votes
4answers
750 views

Replacing a for-loop with something functional

I'm a physics grad and have been using Mathematica mostly for data visualization. The evaluation part I normally do with C/Python, but I've been wanting to try out Mathematica for these tasks, too. ...
2
votes
3answers
134 views

How to insert a Matrix into a larger matrix

I have a 4x4 matrix v1 v2 v3 v4 myM={{a1,a2,c1,c2}, v1 {a2,a3,c2,c3}, v2 {c1,c2,d1,d2}, v3 {c2,c3,d2,d3}} v4 And I want to ...
3
votes
2answers
85 views

Combining sub-matrices by replacing zero elements with symbols

I have a nested matrix as m: ...
6
votes
6answers
231 views

How to check if two nested lists have the same structure?

How can I check if nested lists like these have the same structure: ...
3
votes
2answers
74 views

SameTest issue?

Folks, I am trying to construct and algorithm which finds all of the remaining groupings (of three items, in this case) from a list of items for which no two items are in groups that have previously ...
1
vote
2answers
53 views

Filling a matrix with a list of lists

I have a list of lists with different lengthes: {{a1,a2},{b1,b2},{c1,c2,c3},...} Now I want to create a matrix the following way: ...
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) ...
3
votes
2answers
291 views

Convert a list of hexadecimal numbers to decimal

I know that to change a single number from hexadecimal representation to decimal, you can use: base^^digits. However, if you have a list of numbers, Mathematica ...
2
votes
2answers
66 views

How to apply list of values to a list of functions

I have the following: first= {1+a,2+a,3+a,4+a} and a list t={0,1,2,3} I want to evaluate the first element of "first" at ...
9
votes
2answers
471 views

How do I prune a list of pairs of numbers so that each number occurs on only one pair?

How do I select only the first pair of numbers in which a number occurs from a list of pairs of numbers? For example, I have ...
1
vote
1answer
57 views

Delete duplicates from list of pairs

I'm fairly new to Mathematica, and I've finally stumbled upon something that's beyond my googling powers. I have a list of pairs, where each pair contains in its first entry a matrix and in its ...
4
votes
2answers
95 views

Select sub-lists of common length from a list

Revised Question I have a list with nested lists with the following format: ...
0
votes
1answer
28 views

How to combine two or more groups while selecting form the unbalanced panel data if the number of obs is less than a scalar in certain groups

I have an unbalanced panel data. I want to calculate group statistics for each group. However, if ith group has less than K obs, then I want to combine ith and (i+1)th groups to calculate group ...
13
votes
7answers
762 views

How to sort digits in a string while keeping other characters untouched?

Now there is a string with digits and letters, for instance, "95uge678r3gi89hgfe30kgh063d51". And the expected output is ...
4
votes
5answers
263 views

How do I write a condition for Position that uses both the current and previous element?

For example, given {57, 3, 40, 94, 9, 84, 81, 93, 76, 5, 7, 76, 38, 9, 23, 95, 49, 0, 30, 3} I'd like to get all the indices at which the elements cross from ...
8
votes
3answers
374 views

Turning a set of random walk data 45 degrees

I have a set of data that is just a "random" (generated by me, not by computer) sequence of length 2000 of 1's and (-1)'s. I used it to plot a 1-D random walk where +1 is step up, (-1) is step down, ...
0
votes
4answers
80 views

Find all disjoint subsets of equal length

Suppose that $A$ is a list with $n$ elements where $n$ is even. I want to write a function that returns all pairs $(A_1,A_2)$ where the sets $A_1$ and $A_2$ each have length $\frac{n}{2}$, $A_1 \cap ...
0
votes
3answers
74 views

How to iterate through a list of rules?

Let's consider I have a list of rules: {Aa -> 1/2, Av -> 2/5, Bx -> 3/7, Ce -> 4/9, ...} I want to find all keys that contain the letter "A" and ...