Questions tagged [list-manipulation]
Questions on the manipulation of List objects in Mathematica, and the functions used for these manipulations.
2
votes
2answers
39 views
selective deletions from list
I have a list:
lis = {{"b","x","d"},{"a","z","b"},{"a","x","b"},{"a","x","c"},{"b","z","d"}}
Certain consecutive elements of this list will have identical first ...
0
votes
1answer
54 views
Use iterator outside of iteration
I want to Map something that is depending on an iterator from the outside of e.g. Table into the procedure.
What would be the ...
0
votes
0answers
41 views
Using List to create lists of strings: difference(s) between two one-line codes?
In the Virtual Book of Mathematica, there is a simple example to show how to create lists of strings by List:
...
1
vote
2answers
59 views
How to multiply out the same lists [on hold]
If I have a list of the following form:
{1,1,1,0,1,1,1}
How can I create a list containing 5 of these lists ie:
...
2
votes
1answer
41 views
ReplaceAll rules for Power function
I have the following function:
eW = fL11(u1L^r + u2L^r) + fM11(u1M^r+ u2M^r) + fH11(u1H^r + u2H^r)
The full form of eW is then:
...
9
votes
3answers
246 views
Min and Max of a list of Associations
I am trying to find the minimum values for all elements in a list of associations, below is an example
...
0
votes
1answer
42 views
Count sublists containing certain strings
I have a nested list which looks like:
and I would like to count the following:
all sublists containing {n_,n_} && {n_,n_,n_}
all sublists containing {l_,l_} && {l_,l_,l_}
all ...
1
vote
1answer
52 views
0
votes
1answer
63 views
Access Large Array with Preassigned Index
I wish to use a preassigned variable to index a large array many times. For example:
a = {i,j+1,k-1};
b = {i+1,j,k-2};
I know I can do this several ways but for ...
0
votes
0answers
12 views
NDSolve: Method of Lines: same grids for spatial discretization: error: stiff system_zero step size
How can I modify bbgofrey's answer so as to use $n+1$ grid points for variable $y$? My code
...
3
votes
3answers
68 views
Replacing a column of a matrix
I want to replace a column of a matrix. The best I've been able to come up with is
...
3
votes
3answers
221 views
List Interval Sum
I am doing a large data-set computation. Among those computational steps, in one step I need to do a sum with a pattern: Sum the elements with same interval.
For example, for a list from 1 to 9; ...
0
votes
1answer
44 views
Inconsistent integration results using expressions and unexplained imaginary numbers
Consider the following code (Mathematica 8):
...
3
votes
1answer
63 views
TakeList of a Dataset
Check this out
I want to split the Dataset for graphical reasons, like creating a nice composition on a page, TakeList should ...
1
vote
2answers
49 views
Extracting first 2 elements of table
I have a table in Mathematica as follows:
table1 = {{2,4,51,2017},{20,5,21,2018},{300,1,22,2016}}
From this, I was wondering how one could extract only the first ...
1
vote
2answers
49 views
Numerics & List Manipulation:ListCorrelate: yield $\{-f1 + f2, \dots, -f2 + f4, \dots\}$ from $\{f1, f2, f3, f4, f5\}$
The command
ListCorrelate[{-1, 1}, {f1, f2, f3, f4, f5}]
yields
{-f1 + f2, -f2 + f3, -f3 + f4, -f4 + f5}
is there any simple way to get
{-f1 + f2, -f1 + ...
2
votes
2answers
94 views
Efficient way to join elements under a conditional
I am solving a certain challenge given by my friend.
I want to print the first day of the year if it is not a leap year, while I want both first and second days if it is a leap year.
I want to know ...
0
votes
4answers
62 views
How to check if every element of a list satisfies a condition inside an IF construct?
I have the list,
listx = {{0., -0.6}, {0.08, -1.}, {0.16, -0.9}, {0.24, 1.}, {0.32, 0.6}}
And I want to check if every second element satisfies both conditions ($...
3
votes
2answers
61 views
Dropping lists using pattern [duplicate]
I have the following list of lists.
data = {{0, 0, 0}, {1, 0, 0}, {2, 0, 1}, {3, 0, 0}, {4, 0, 0}, {5, 0, 3}}
I want to drop all the lists with ...
0
votes
0answers
21 views
Method of Lines: discretization: error that “part 101 of …( list)… does not exist” seems to disappear [closed]
In bbgodfrey's answer discretization of
$$ \partial_z x=w $$
is implemented by means of
...
13
votes
2answers
645 views
Delete with multiple indices is extremely slow--workaround?
Delete is unbelievably slow when deleting multiple elements from a non-packed array.
Is there a robust workaround that will work on any non-packed array?
...
3
votes
2answers
149 views
Basis enumeration of large lists
I want to combine two list in the following way without using Table or any loop structure.
...
0
votes
1answer
55 views
5
votes
4answers
425 views
2
votes
1answer
83 views
How to compute Maximum Drawdown faster and highlight data-list-line on the plot?
Given a list as
...
2
votes
1answer
22 views
combine a list with && [duplicate]
I have a huge list of the form
{a==1,b==2}
I want to get the expression like
a==1&&b==2
How is it possible to do ...
2
votes
3answers
68 views
How to create a list of six unit vectors in 3D?
I want to have a list {{1,0,0},{0,1,0},{0,0,1},{-1,0,0},{0,-1,0},{0,0,-1}}. How to generate it smartly?
1
vote
1answer
41 views
How can I know the value of parameters?
In the the attached image I plot two function for the parameter $a1, a2, a4$. I take $a2$ as particular value, $a1$ as discrete set and $a4$ continuous value. In the plot how can i recognize for which ...
2
votes
1answer
86 views
For loop within GeoGraphics
I'm trying to plot a map with a list of destinations as Disks.
I first input the cities into a list such as:
...
4
votes
1answer
67 views
String Join but not fully
Suppose I have the following string list:
l={{"a","dog"},{"the","pen"}}
how can I turn this to
{{"a dog"},{"the pen"}}
I ...
3
votes
4answers
102 views
Testing intersections in a list
In the following list {{1,3,5},{2,4,5},{3,4},{1,5}}, two elements have an empty intersection. This is not the case of the list ...
3
votes
2answers
146 views
How to drop certain elements in certain positions from a list using drop function
a = Table[i, {i, 1, 10}]
Drop[a, {5, 8}]
If go with the above procedure, It will delete all the elements from between position 5 to 8. How to drop elements which ...
0
votes
0answers
19 views
ListLinePlot Manipulate only discrete values in Slider
When you use a slider control for any kind of list plots slider should only take integer values and I can specify that with start point and end with step size. However, you can expand the slider and ...
1
vote
1answer
31 views
Multinomial must receive a machine size number
I need to use the multinomial distribution.
In a certain step, by coincidence, the input probability vector is ...
5
votes
6answers
423 views
How to multiply nested lists by a list with the same length?
Here's the expected output:
{{a, b}, {c, d}, {e, f}} * {3, 4} = {{3a, 4b}, {3c, 4d}, {3e, 4f}}
However, the code above will multiply each element of the ...
3
votes
2answers
110 views
How to generate a “value-frequency” table with random numbers?
I want to create a "value-frequency" table from the following expression.
Counts[Sort[RandomInteger[{1, 5}, 500]]] // TableForm
The generated table should be in ...
1
vote
2answers
51 views
1
vote
1answer
20 views
-1
votes
1answer
50 views
Problem with Do [closed]
Good day, I want to assign some values in a list as in the following way:
The problem is that when I run the program, it does not assign any value to alpha. Does anyone know why?
Thanks for your help
1
vote
2answers
66 views
Quick cursoring and replacement over a list
I have an initial list which is partitioned as follows.
...
2
votes
0answers
35 views
Fold/ NestList/ etc in MCMC loop for optimisation
I am trying to simplify and optimise an old loop code I wrote. Since Fold and NestWhile use the results of the last iteration in the new iteration, I would like to use them in order to get rid of Do ...
1
vote
1answer
21 views
Splitting a list of letters into subsequences starting with uppercase letters [duplicate]
Given a list of upper/lowercase characters, I'm trying to split it into subsequences that start with an uppercase and contain the next few (not necessarily positive number of) elements up until the ...
1
vote
2answers
55 views
2
votes
2answers
42 views
Flattening a list desiring a specific format
Suppose I have the following list:
l={{{1},{2}},{{3}},{{4},{5}}};
How can I flatten this such that I get:
...
2
votes
2answers
148 views
How to find second,third,etc maximum peak of list
I need to find all values of peaks.
I have Table with 10000 elements in it and I plot a graphic using ListPlot.
Then I tried to ...
1
vote
1answer
29 views
Replacement into a list
I have the following polynomials:
pol = {x^2 + 2 x^3 + 4 x^7, x + 2 x^5 + 4 x^6, 3 x^6 + 2 x^9};
and following list
...
0
votes
0answers
39 views
0
votes
1answer
29 views
Making a List For Use in an Integral
I have an equation of the form
$R_{min}+t= R_{min}\, e^{R_{min}}$
where for every time $t$ there is a corresponding position $R_{min}$.
How can I complete the integral
$F(t)=\int_{R_{min}(t)}^{r(...
4
votes
1answer
145 views
Efficient way to add new rules to a sublist within a nested list of rules
I often build nested lists (as a way to keep data sets organised) with some form like:
...
4
votes
2answers
134 views
Partitioning sublists based on positions, with new partitions immediately following original sublist
I need to restructure this list nums:
...
