Questions tagged [list-manipulation]
Questions on the manipulation of List objects in Mathematica, and the functions used for these manipulations.
5,821
questions
1
vote
1answer
6 views
NextKSizePartition, or how to partition a set into subsets of size $k$ but incrementally
This question might seem very much like the linked one below but it differs in a very special way; Mr.Wizard suggested I start a new post:
Partition a set into subsets of size $k$
What I want is to ...
1
vote
1answer
12 views
Converting coordinates in $\mathbb{R}^2$ to a point in $\mathbb{C}$ (and back again)
I have a list of control points for a BezierFunction. I want to apply a function taking input a complex number to these points and then plot the BezierFunction of the resulting points. I'm looking for ...
4
votes
3answers
143 views
Delete a whole nested list if one of the values in that list contains an “Indeterminate” value
I'd like to delete a whole nested list if one of the values in that list contains an "Indeterminate" value.
The link below provides a solution to delete individual "Indeterminate" values:
Delete ...
5
votes
1answer
51 views
Delete rows by testing multiple columns againts a range of test values
If I have a matrix or table of data,
...
1
vote
0answers
30 views
How to compute the multiplicative order of an element in a finite field
I want to find the multiplicative order of say the element {0,1,0} in GF[8].
I made a list:
b = Map[GF[8][#] &, Tuples[{0, 1}, 3]]
I tried:
NestWhileList[b[[3]]*# &, b[[3]], # != b[[5]] &...
1
vote
1answer
44 views
How to Make Table Headings [duplicate]
In the code below, how can I add (left to right) column headings "n", "pp","aa"? There is also a shift in the alignment across the generated rows.
...
1
vote
2answers
35 views
Apply NestList to Iteratively Calculate Gradient (Gradient Descent)
I'm attempting to calculate the gradient of a function defined by two variables.
After following a tutorial I found, I have the following code:
...
1
vote
0answers
46 views
How to assign a nested list indices for later use
In an attempt to calculate a summation dependent upon a nested list it appears that it a simple use of [[{n,k}]] does not yield the desired result. For example with ...
0
votes
2answers
93 views
SmoothHistogram doesn't appear to work
I have a data set with 500,000 elements. I am trying to use SmoothHistogram to plot the distribution, but it doesn't work and the kernel quits. I used R on the same ...
0
votes
1answer
37 views
Search for certain entries in an expression
I have a list with large expressions. I would like to find certain functions and their derivatives by searching the list. The search outcome should be the functions/derivatives found only, not the ...
2
votes
1answer
56 views
Filtering data 'geometrically'
I was looking at a very nice answer here, where the question was applying a confidence region to some data.
If we plot some data as a scatter plot:
...
2
votes
1answer
69 views
Fastest way to compute determinants over (lists of) machine precision numbers
The below code is a code snippet of a larger project of mine. The project is mostly optimised but this part is not. I'm struggling to improve it, the code takes a really long time to evaluate for what ...
0
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0answers
40 views
What is the meaning of [ ][[ ]]? [duplicate]
I have a question about these two pieces of code
Reap[
For[i = 1, i < 10, i++, Sow[i]; Sow[i^2]; Sow[i!]; Sow[N@Log@i]];
][[2, 1]] ~ Partition ~ 4
and
<...
0
votes
3answers
35 views
Making tuples with values produced by `Range[n]` and a constant $m$
I'd like to produce a list of $n-$tuples made from the elements of Range[n] coupled with a constant value $m$.
Here's an example, given $n=3$:
...
1
vote
1answer
42 views
Padding behavior
Why does ArrayPad[Range[7], 4, Padding -> {1, 2, 3}] return {2, 3, 1, 2, 1, 2, 3, 4, 5, 6, 7, 1, 2, 3, 1}?
I expect it to ...
0
votes
1answer
65 views
Phase unwrapping
I am facing a problem in unwrapping a phase.
I have a data set presented by $a_i$, where $i$ varies from $1$ to $N$. I need it as follows:
If $\mathrm{abs}(a_{i+1} - a_i) > 3$, add $6 k \,$ to $a_{...
4
votes
3answers
226 views
6
votes
7answers
459 views
0
votes
1answer
28 views
How to get a function from a list element? [duplicate]
I have a set of arguments in a list like:
uy = {21/2 + y/2, 13.6667 + 0.666667 y, 20 + y}
Now, I want to assign a function (call it 'f(y)') to an element of that ...
1
vote
2answers
23 views
0
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0answers
15 views
Can I use Postfix with a condition [duplicate]
I have a nested list Data set with mostly numbers, there are a few elements that occur as strings that I want to convert to a number. By postfixing ToExpression I ...
2
votes
1answer
33 views
Calculate and plot mean values of pairs of data points
I have a list of data points where there can be multiple y values for a given x value, e.g., {{0, 4}, {1, 2}, {1, 3}, {2, 3}}. I would like to
Take the mean of the y values for each x value. Get a ...
1
vote
0answers
35 views
3
votes
1answer
40 views
Order or function/list arguments in map/select/others
I keep being uncertain of the correct order of [function,expr] arguments to functions such as Select, Pick, Cases, Position, etc., because I'm used to the ...
2
votes
1answer
27 views
Using the value of OptionValue to clear a list
I'm currently using OptionValue inside a function, the Option I passed to the function should be cleared, then populated with ...
1
vote
1answer
26 views
Manipulating variables indexed by a list
I have a variable g, indexed by a list:
g[{1,1}]=11;
g[{1,2}]=12;
g[{2,1}]=21;
g[{2,2}]=22;
I would like to move things around as follows:
...
0
votes
1answer
29 views
Picking out elements from a multi-level list
I have the following problem that is giving me headaches: I have a list with the elements in the following form:
{x,{{a1,b1},{a2,b2},{a3,b3}}}
I would like to ...
1
vote
1answer
56 views
Is there a function or a way of getting a remainder or modulus with equations with “surds”?
So I'm working with "surds", or radicals. I have expressions like
$$7 + 5\sqrt{2} + 6\sqrt{3} + 7\sqrt{6}\tag{1}$$
and I want to take the "coefficients", for lack of a better word, and take their ...
1
vote
2answers
54 views
How can I count only the sublists having more than 9 number of '2'?
I made a table giving me 1's and 2's
In[23]:= S = Join[Table[1, 1], Table[2, 1]]
Out[23]= {1, 2}
And then I made it bigger:
...
3
votes
1answer
61 views
How to access all instances of a defined function
This should have a simple solution, but for some reason I cannot find how to do this.
Let's say I have a "function" where I have defined values (in my actual example I have many instances of this, ...
0
votes
0answers
27 views
Creating a special product function
I am having trouble working with lists inside functions with Mathematica. Basically, I have a list of numbers and a special way to multiply them. I want to have a function that is able to create a ...
3
votes
1answer
96 views
Why doesn't DeleteDuplicates do what I want
First off. I am not a mathematician I am a linguist, a syntactician who is trying to say something about semantics, which in the case at hand can be largely understood to reduce to set theory. That ...
0
votes
1answer
29 views
I need to extract data from a multi-valued functions and interpolate them into separate single values functions
The graphed data look like this. I need to extract the data for each curve individually and use Interpolation to create a differentiable function for each curve. Can you show how to do this?
I will ...
1
vote
1answer
44 views
How to extract and plot pieces of a multi-valued function
I have multi - valued functions that create lists of data like this:
...
0
votes
1answer
50 views
How to generate a list with elements f[i] for a function of several variables f?
I would like to create an array of length n with each element i equal to the function
...
2
votes
1answer
111 views
Extract values of a ListAnimate plot that are moving at a fixed rate
I have this code which animates a layer of fluid moving on the outside of an ellipse with a moving black point on the cylinder surface itself.
Is there a way to find the value of the blue outer line ...
0
votes
1answer
55 views
How to flatten a tensor product
Say I have a tensor product of four two dimensional spaces
$\Lambda = S\otimes S\otimes S\otimes S$. The basis of $S$ is CB={{1,0},{0,1}} . I generate the ...
0
votes
1answer
35 views
Delete element from list [closed]
I have a list with 1000 elements, and I want to delete all elements from index 400 (including) until the last element.
7
votes
1answer
101 views
Partitioning a list by cumulated sum when the accumulate reaches a fixed value
I have a list dat = {10, 10, 10, 10, 10, 40} .
When the cumulative sum of dat reaches >=...
4
votes
1answer
78 views
Select sets from a list which are in ascending order
Given a list of sets I want to choose the sets whose elements are in ascending order. I think I need to use: Select[list, crit] for this problem, but I could not ...
2
votes
1answer
41 views
Use a list with single number for the second input of Table
As you see both inputs below give the same results.
Is there any reason to use List[3] instead of just 3 in the first case?
<...
3
votes
2answers
95 views
When do functions apply on lists and when they do not
I have read in my lecture notes on Mathematica that functions (in the general sense) can be applied to lists of data and that they can return new lists with data. I have tried this and I have got ...
3
votes
2answers
96 views
Remove a list element based on condition
I have a list with many expressions as elements. I want to remove the list elements which do not contain certain variables. For example, I would like to remove the element which does not contain ...
2
votes
1answer
57 views
Tuples with more criteria
I have seen that there is question here which does almost what I wanted to ask but it's not quite what I wanted.
Efficiently generating tuples with Outer
What I would like to have is a Tuples of a ...
1
vote
2answers
35 views
Manipulation replacements rules from Solve [closed]
Assume the call to the routine Solve[eqn==0,{x1,x2}] returns:
{{x1->a1,x2->a2},{x1->b1,x2->b2}}
I would like to ...
2
votes
1answer
30 views
Taking Out Max List from List of Lists
I have a list like this:
L1 = {{500, {x->3, y-> 4, z -> 1}}, {110, {x->11, y->41, z -> 9}}, {750, {x-> 1, y->-1, z->0}}}
Is there a ...
0
votes
2answers
28 views
How to create seperate empty lists assigned to seperate variables
Instead of doing
l1 = {}
l2 = {}
Is there a way to incorporate a loop to make this process faster?
2
votes
2answers
49 views
How to iterate through a lists of lists and delete a certain element?
Say I have a list of lists such as
l1 = {{a, 2}, {a, 5}, {b, 3}, {b, 9}}
How would I iterate through the list and delete all the lists with the first element b ...
0
votes
1answer
41 views
How do I split up a list of data points into invervals and assign values to those intervals?
So I have a data set for chess and our goal is to plot the difference between the rating difference versus white's win rate. I want to subdivide the x-axis into intervals like (-10, 0) (10,20) (20,30)...
3
votes
1answer
47 views
How to add ± to each element in the List?
I just want to add ± with Function Thread
Output that I want
{±1, ±2, ±3, ±5, ±7, ±9}
...
