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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1answer
46 views

Selecting last partition in integer partition [closed]

I want to get the last partition from an integer partition. For example: IntegerPartitions[8, {3}] ...
1
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2answers
141 views

Doing same operation on multiple files

Is there a way in mathematica to do same operation on multiple files at once? And preferably have the output in a table or list form? I want to do the following operation preferably in few non-labor ...
5
votes
3answers
191 views

How to find the right permutation, which fits to the problem?

I'm new here and I hope I can find some help. I'm from Germany, so sorry for my English. I look for a number, whose digits are all different. It isn't known how many digits it has. But there is a rule:...
0
votes
1answer
72 views

Extract all elements of an expression in order into a list [closed]

I have and expression a + b + c - d and I would like to generate a list of {a, +, b, +, c, -, d}. I have tried ...
4
votes
1answer
140 views

How to transform a list (of sums) into list of summands

Suppose you have the list list={a,Sin[b+c],d+c}. What I want is to transform all elements of list with head ...
1
vote
1answer
117 views

Summation over list elements

As we know, one of the simplest way to do a summation (with special intervals) over list elements is using Sum[list[[i]], {i, 3, 8, 2 }] (*with steps of 2*) for ...
0
votes
1answer
134 views

Combining two tables and highlighting certain values

I have got a variable list: ...
11
votes
4answers
184 views

Faster position-based duplicate removal in a ragged array?

Take a ragged 2D array: rArray={{4, 2, 1, 0}, {2, 2}, {0, 0, 3, 3, 3}, {4, 0}, {3, 4}} I need to "deduplicate" this, where a duplicate is any element of a ...
0
votes
1answer
100 views

Eigenvalues and Eigenvectors Order [duplicate]

Say I have a list of eigenvalues and eigenvectors produced from a matrix $M$ using the command {eig1,eig2}=Eigensystem[M], which will return the eigenvalues with ...
0
votes
4answers
236 views

Cases vs Select, Pattern vs Pure function [duplicate]

What is the difference between having Cases with selection condition presented by pattern and a with pure function as condition? ...
2
votes
1answer
67 views

3D-Plot of a list of complex numbers and a list of real numbers

I'm a newcomer to Mathematica, and I'm having trouble with the following question. Say we have a list of complex numbers list1 and a list of real numbers ...
4
votes
1answer
124 views

Recursive list contruction

I am attempting to implement the exercises from The Little Schemer in Mathematica, and running to a bit of a challenge with rember (remove member). Given a list and a value, the function just returns ...
6
votes
5answers
197 views

Removing elements from a nested list based on their global count

I have a very large table containing sublists, such as for instance: {{1, 2, 3}, {4, 5, 6, 7}, {1}, {1, 8}, {9, 10}, {11, 6, 12, 13, 14, 15, 16}} I want to ...
14
votes
2answers
252 views

Fastest way to sum the upper triangle

I feel like this is an recurring question: if there's a symmetric matrix whose diagonal is not all 0, how could I get the sum of the part of it that's above the diagonal as fast as possible? Small ...
12
votes
1answer
610 views

When to use @@@ vs. /@ [duplicate]

So much thanks to Szabolcs in improving sequence.. for complete explanation. I am so glad to read all explanation which fundamentally remove the problem. But in number 4 of its explanation pointed to <...
6
votes
2answers
440 views

delete zero rows in a matrix

If there is a matrix with some of its rows equal to zero: (its zero rows are randomly distributed and does not have an ordered arrangement): same as: ...
1
vote
1answer
51 views

Adding up a list of subscripted elements [closed]

I have a list of entries with subscripts. I want to add just the entries. How can I do that in the presence of subscripts? For example: list = {1a, 2b, 3c} And ...
3
votes
3answers
100 views

How to compare and remove x-coordinates (and the associated y-coordinates) that are less than previous x-coordinates?

I am using Mathematica version 9.0 and am trying to compare and remove x-coordinates, and the associated y-coordinate, that are less than previous x-coordinates. Below is an example using sample data. ...
1
vote
1answer
55 views

Deleting duplicates of plus or minus symbolic quantities from a list [closed]

Let's say I have a list l = {a + bc - d, -a - bc + d, a + b};. Now I want to apply DeleteDuplicates[l, crit] to this list, such ...
3
votes
3answers
198 views
1
vote
0answers
54 views

Transform a vector DE into a set of scalar DEs [closed]

I have the vector equality: {{a,b},{c,d}}.D[{x1[t],x2[t]},t]=={{e,f},{g,h}}.{u1[t],u2[t]} I want to solve this using DSolve. ...
3
votes
1answer
53 views

Saving Dot-ed eigenvectors in a special comparison

We have produced a 4*4 matrix in any iteration containing nx from 0 to 2 by steps of 0.5. and in any iteration we have saved sorted orthogonalized-eigenvectors based on their eigenvalues with this ...
5
votes
2answers
253 views

Displaying a list of percentage values according to their classification

I have a list of percentages as follows: percent = {21.15, 42.3, 57.68, 73.06, 84.6, 90.37, 96.14, 99.99, 99.99, 99.99, 99.99} I want to classify these ...
0
votes
2answers
336 views

“Part specification is longer than depth” warning in Position function [duplicate]

I'm working on a project which analyzes financial data. I download the price and dividend information for the SPY ETF which tracks the S&P 500: ...
1
vote
2answers
92 views

How to find the same number in sublists of list

Intersection[Table[Table[Sqrt[p1]/r1,{r1,0.1,0.7,0.1}],{p1,0.5,5,0.5}]] I am trying to find same numbers in the sublists. But Intersection is not working for this....
1
vote
1answer
69 views

calculate relationship between cause and effect (rows/columns/delta etc.) on tableform

I tried to enter this Excel (on the right of the picture) information to program. following these codes has been used: ...
2
votes
2answers
161 views

Efficient List of Lists

I'm running some analysis that requires the creation, row by row, of a large list of lists. The big list is called "Nodes" and it will ultimately contain hundreds of thousands of rows. The first few ...
6
votes
2answers
76 views

How to count the number of values in a discrete function?

I have a discrete function of an integer variable $n$ defined like this : ...
4
votes
4answers
264 views

Replace matrix rows conditionally while avoiding For loop

I have the following variables: myMatrix={{0,0,0},{0,0,0},{0,0,0},{0,0,0},{0,0,0},{0,0,0}} myIndices={1,3} I need to replace the rows ...
-1
votes
1answer
56 views

Position not working? [closed]

I have the list: myList={0,0,0,a,b,c,0,0,d} I need to find the positions of all elements that are non-zero. I do like this: ...
6
votes
1answer
94 views

Problem Using Evaluated Replace with Associations

If I define some function like: toISOdate[data_List]:=DateString[data,{"Year","-","Month","-","Day"}] and try to applicate it in an ...
5
votes
3answers
252 views

How to imitate list comprehensions for constant arrays?

In Python, ['a'] * 10 generates ['a', 'a', 'a', 'a', 'a', 'a', 'a', 'a', 'a', 'a'] and ...
4
votes
2answers
61 views

Inputting values into the variables without having to input the matrix all over again

I'm practicing using LU decomposition on Mathematica. I am able to find the L & U matrices, specifically the variables. However, i find it tedious having to input the newly found values and form ...
0
votes
1answer
70 views

Count participation of variable list

I have the directed edges of a graph given by a list of variable (vertex) pairs. ...
2
votes
1answer
64 views

How to extract part of association?

Considering an association: asc = <|"a"->1, "b"->2, "c"-><|"e"->3, "c"->4|>, "d"->5, "e"->6, "f"-><|"g"->7|>|> How ...
5
votes
3answers
250 views

List all “duplicate” elements in Tally

Tally[list,test] can use a custom function test to judge if elements are equal. But the output will only give the first element ...
2
votes
1answer
121 views

How can I write a loop to get many values from a solution?

I am looking at the value of x[t] at day t = 200 over several years. I tried to do it using a For-loop but it didn't work. This ...
3
votes
2answers
82 views

Find sub-sets of vanishing additions or subtractions from a list?

Let's say I have a list L containing n numerical numbers. Now I want to find all sub-sets of ...
2
votes
2answers
256 views

Import a column of data, make a matrix from it and export it WITHOUT curly braces

I'm new here and with Mathematica, too. I want Mathematica to import data from a txt file (it has one column of data). These entries are z-values. From this I want to make a matrix - 508 entries make ...
3
votes
3answers
160 views

Find position avoiding For loop

I have a list: {a,b,c,d,e,f} And a function sizeFunc[element_] which returns the size ...
2
votes
1answer
67 views

Dropping rational coefficients

I have a list of expressions (they all are exact numeric quantities, not containing any variables), some of them have integer or rationals coefficients, or complex coefficients with rational or ...
1
vote
0answers
32 views

Accessing the elements of a list of values [closed]

I have a list of polynomials (all with the variable x) called lyle and a function that accesses this list and evaluates it at ...
2
votes
2answers
114 views

Replace elements in some region in a list

I want to replace some elements in list. Assume that we have A={{1,2,3,4}, {5,6,7,8}, {9,10,11,12}, {13,14,15,16}} and we want to replace elements <...
1
vote
1answer
66 views

Sort and Save Matrices Eigenvectors to a Larger Matrix

We are going to sort and save all orthoginalized-eigenvectors of 4*4 random matrices (produced in any iteration) to a larger matrix such as storagematrix. Since, produced random matrices are 4*4, ...
0
votes
1answer
182 views

Match a variable name pattern [duplicate]

I have a list of variables: {RBI,RCD,ASD,FGH} I want to select only those whose name starts with R. Using the pattern Rx_ ...
2
votes
3answers
156 views

Join nested lists based on first and last elements within each list

I have a nested list like this: test1 = {{1, 3}, {1, 4}, {1, 7}, {2, 1}, {3, 5}, {4, 1}, {5, 2}, {6, 1}, {7, 6}} I want to join the lists together depending on ...
1
vote
3answers
155 views

Identify a scalar, a list

I have a symbolic scalar m2 and a symbolic list (representing a 3x3 matrix) A. I want a function which does something like: <...
1
vote
2answers
78 views

Convert a list of lists of rules to a list of values [closed]

I have a list of the following form: thisVeryExcitingList={{x->1},{x->2},{x->3}} I would like to convert it to the form ...
3
votes
3answers
204 views

Move element inside a list

I need to change the position of a single element in a list. Example: I start with: {a,b,c,d,e,f} I want to move the a before ...
7
votes
4answers
245 views

Improving a selection routine

How can this code for extracting the smallest (absolute) real value be improved? and would it be simpler using associations? ...