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

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6
votes
5answers
257 views

Removing reverse versions of lists from a nested list [duplicate]

I need to remove the reverse versions of lists from list of lists. I.e.: {{1,2},{2,2},{2,1},{a,1,2},{2,1,a}} I need to reduce to ...
6
votes
7answers
345 views

Sum of two functions, list processing

I am creating some simple graphs of functions defined by ordered pairs. Students are learning about "operations on functions", in this case, adding functions. If I have two functions defined by ...
6
votes
1answer
478 views

ReplaceAll inside an Iterator

I'd like to apply a set of rules to an expression defining the iterators of the table, like this: ...
5
votes
4answers
220 views

How can I get a list of the positions of the running minima in a list?

I want the positions of the (sequential) running minima in a list, that is, the positions of entries that have the minimum value of all the elements in that list, up to and including that entry. For ...
5
votes
4answers
189 views

Signed power set of a list

Given {a, b, c, ...} with $n$ elements generate a list with $2^n$ elements. For example, if the list were {a, b, c}, then the ...
5
votes
3answers
268 views

Element-wise list operation on list of lists [closed]

Suppose a function F operates on list A: $$A=\{a_1, a_2,\cdots, a_n\}$$ I have a list of lists, B: $$B=\{A_1, A_2,\cdots,A_m\}$$ Is there a syntax to specify that F should operate on members of B, ...
5
votes
2answers
104 views

Comparison Operation for Nested Matrices

I have a nested matrix n as bellow ...
5
votes
5answers
418 views

Counting 'False' values at the ends of a list

I have table like this: t = {False, False, False, 4.5, 6.789, 1.23, 0.98, False, False} and I want to know how many False values I have at the beginning and at ...
5
votes
6answers
304 views

Convert array from {{…}} to “[[…]]”

I have made this function: conv01 = Map["["<>StringJoin@@Riffle[#,","]<>"]"&,Map[ToString,#,{2}],{0,1}]& to convert: ...
5
votes
4answers
192 views

How to delete mirror symmetric point pair efficiently

Look at following pic There are five points, I can generate the following point pairs ...
5
votes
2answers
225 views

Ranking a vector containing ties

How can I rank a vector such that the ties are replaced by their middle ranks. For example, {1, 2, 2, 3}. I want to rank this vector but the ties must be replaced ...
5
votes
1answer
751 views

All possible topological orderings of a graph

TopologicalSort[] returns one of many unique orderings. From wikipedia: if a topological sort does not form a Hamiltonian path, the DAG will have two or ...
5
votes
1answer
229 views

Selecting a list from a list of lists

In working through Programming Paradigms Via Mathematica (A First Course) I have come across this two part question: A permutation of length "n" is a list of the first n positive integers in ...
5
votes
1answer
176 views

What is the fastest way to maintain a large set of expressions?

In my algorithm I need to maintain a set (an unordered list of distinct elements) of expressions supporting two operations: Test an expression for membership in the set Adding a new expression to ...
5
votes
5answers
2k views

How to sum over a List

list = {11.5575, 11.397, 5.52734, 4.0878, 2.54815, 1.86652, 2.55028, 2.14952, 1.6242, 1.34117} I have a list of numbers. How do I make a function that creates a ...
5
votes
1answer
425 views

Numbering element in descending order

How can I numbering the elements in descending order of second elements of sublists? For example, if I have the list which is ...
5
votes
6answers
327 views

Creating sums of elements from a list

I have a list $(d_1, d_2, .. d_k)$ and I want to create all sums that I get for adding only two elements for my list $(d_1+d_2, d_1+d_3,...d_{k-1}+d_k)$. The ...
5
votes
2answers
1k views

Converting numbers to integers

I've read the available documentation but I still haven't found an NumberForm -> Integer function yet. No result in this site's search, either. Does it exist? ...
4
votes
1answer
95 views

Parsing string with nested information

I am trying to parse a string, but I have no idea how to solve the following problem ...
4
votes
2answers
75 views

How to keep first observation and delete other observations of each group in unbalanced Panel data

I have a huge panel data. I want to create a new data keeping only first observation of each group. How can I achieve it? For illustrative purpose; ...
4
votes
3answers
137 views

Extracting columns from multidimensional list

Perhaps a very easy question but I posted this on the Wolfram Community and didn't get any answer.. Suppose I have data like: ...
4
votes
2answers
136 views

Sorting out atom types in an XYZ file

I am trying to rewrite the output of "VertexCoordinates" such that instead of a hybrid list of atoms and coordinates that result from using the following input program, I want all coordinates of the ...
4
votes
3answers
263 views

How can I change a list to a sequence without destroying nested list

I defined a function f like f[x___, y_] := something; and if xs and ...
4
votes
2answers
570 views

What is the Mathematica way of joining two tables?

Is there a special Mathematica way of joining tables of data together, so that I would get similar functionality as if I was running a database with sql? For example, I have one particular table ...
4
votes
1answer
172 views

How do I randomly select 'k' positions in a list and shuffle their respective elements without effecting the other elements?

Imagine I have some list: listA = {"a","b","c","d","e","f","g","h","i","j"}; I'd like to randomly select k positions in the ...
4
votes
3answers
504 views

Finding elements from a sparse matrix

I am dealing sparse matrices of very large dimensions. I need to locate the positive and negative elements of the matrices and make lists of their corresponding positions. Of course I can write a ...
4
votes
2answers
124 views

How to constrain the generation of all possible orderings?

Here is code from Simon Woods' answer for getting all possible weak (equal ranks allowed) orderings for $N=3$ objects: ...
4
votes
1answer
130 views

Timing Total crashes kernel

Here is a simple test function test[n_] := Module[{i = 0}, Total[Nest[{++i, #}&, {0}, n], -1]] On my system V9.0.1 running OS X 10.6.8 and with a clean ...
4
votes
1answer
175 views

List manipulation - various

Update OK, Please forgive the messiness of this, but I am working with something like: ...
4
votes
7answers
697 views

Finding the midpoints of an ordered list of numbers

Suppose that I have an ordered list of numbers. The numbers in the list may be evenly spaced, but they may not be. Here are two examples, list1 and ...
4
votes
2answers
521 views

Removing not-a-number entries from an array of numbers

I have a list of {x, y, z} coordinates from a wavefront sensor I'm working with. However, not all of the imported points have actual values, but they still get ...
4
votes
1answer
388 views

Create a table with inline conditions

I am trying to create a table with conditionals inline. For example, I'd like to create a 2 dimensional table like this: ...
4
votes
3answers
395 views

Preparing data for making an ErrorListPlot

I often have the following notebook in Mathematica, which I use to make a dataset and associated errors: ...
4
votes
2answers
269 views

Partition a set into $k$ non-empty subsets

The Stirling number of the second kind is the number of ways to partition a set of $n$ objects into $k$ non-empty subsets. In Mathematica, this is implemented as ...
4
votes
1answer
279 views

Use single ListPlot for multiple sets of data (on separate graphs)

This is the code I have working for a single set of data. Is there a way I can structure this to have multiple sets of data? ...
4
votes
3answers
1k views

How to replace all occurrences of an element in a list?

Consider the following: list={1,2,2,2,3}; I would like to replace all 2 with the string "Test". ...
4
votes
1answer
620 views

How do I treat elements in a list as variables inside a module?

I want to be able to assign values to a list element inside a module. For example if I have: ...
3
votes
1answer
142 views

Functional programming approach to avoid traditional loops

I'm currently learning from the wonderful post: Where can I find examples of good Mathematica programming practice? And i'm correcting my habits using Nest/Map/Thread instead of loops. The problem ...
3
votes
3answers
187 views

Pare down list recursively

What is the best way to pare down a list whereby the $n$th number is removed from the list recursively? This ...
3
votes
2answers
254 views

Weird behavior when changing parts of matrix

I have this matrix: mat = {{1, 2, 3, 4, 5}, {6, 7, 8, 9, 10}, {11, 12, 13, 14, 15}, {16, 17, 18, 19, 20}, {21, 22, 23, 24, 25}}; and here are its second row ...
3
votes
5answers
232 views

Take the next element in a nested list

My problem is the following: Consider a list of elements. To better understanding my following explanations, I would take this example: ...
3
votes
1answer
123 views

Sectional averages of a list

I am working in Mathematica. I have a table of 200 elements. I want to calculate the mean value for the first 20 elements, for the second 20 elements and so on, up to 200. I will get a table (matrix) ...
3
votes
2answers
668 views

How can I scale the y axis?

I have a file I import and read into a table of $2 \times n$. I can plot this data using the following code: ...
3
votes
2answers
142 views

Change all values of a series to positive values

I would like to change all values of a series to positive values. I refer to my previous question, answered in the most part, very elegantly by RunnyKine. However, there remains a slight glitch that ...
3
votes
2answers
157 views

Using list elements in TrackedSymbols for Dynamic

During the execution of the following code a column of three lists and two sliders are displaying in output. The first list updates if either a or b changes. The second list updates only if the value ...
3
votes
0answers
67 views

Listing all combinations produced by picking one element from each of several sets [duplicate]

I have a problem like this, I am given the following sets {a,b,c}, {d,e,f}, {h,i,j}. I want to pick one element from each set, and output a list of all the ...
3
votes
2answers
106 views

Linear interpolation of a list between periodic anchorpoints

I have a list of the form: list = {1,1,1,2,2,2,3,3,3,4,4,4,7,7,7,19,19,19}; Where we can see that there are an ordered set of integer values that repeat ...
3
votes
1answer
587 views

A rotation-like transform on a matrix

Do not be confused with comments, those are for previous version of the question - Kuba Imagine I have a matrix of the form: ...
3
votes
1answer
145 views

Combining the items with common available dates from two lists [duplicate]

I have two lists of data including dates such as data1 = {{{yy, mm, dd}, a}, ...} data2 = {{{yy, mm, dd}, A}, ...} There are some missing dates from each list, ...
3
votes
1answer
158 views

Little problem with Through

list = Partition[Range[20], 5, 5, 1, {}] {{1, 2, 3, 4, 5}, {6, 7, 8, 9, 10}, {11, 12, 13, 14, 15}, {16, 17, 18, 19, 20}} ...