Questions tagged [indexing]
The indexing tag has no usage guidance.
24
questions
5
votes
1
answer
145
views
Creating a list of conditions
I am trying to create a list of conditions using Table[] in the following way:
...
- 1,063
1
vote
0
answers
88
views
How to index a Table of Lists? [closed]
SOLVED: Thanks to Daniel below, I should index as expected as [[All,All,1] for er etc. My mistake came as I was trying to index from 0, which Mathematica does not like!
I've spent a while reading ...
- 113
4
votes
1
answer
101
views
Search speed of downvalues when indexing with strings
I'm writing a lot of print functions for different parts in a package and at the moment am using something like
myprint[ identifierString_String ][ data_ ] := ...
...
- 1,032
0
votes
1
answer
45
views
How can I merge indices, such as converting a $4$-index list to $2$-index matrix, $C_{ijkl} \rightarrow D_{(ik); (jl)}$?
How can I merge indices, such as converting a $4$-index list to $2$-index matrix, $C_{ijkl} \rightarrow D_{(ik); (jl)}$? This example sometimes appears in physics applications.
Here, I mean $(ik)$ as ...
- 159
2
votes
0
answers
138
views
Part::partd: Part specification is longer than depth of object (Simple list) [closed]
I know that this question has already been asked (I searched for answers), but in every thread I saw the code was much more complicated than what I'm trying to do, and I can't understand why this ...
- 31
18
votes
1
answer
347
views
Intelligent text search on large directories of notebooks?
I have a (deeply nested) directory containing 10s of thousands of wolfram files (mostly notebooks (nbs), but also scripts (.wls), packages (.m, .q
wl), my and wxf data) and many subfolders each with a ...
- 30.6k
4
votes
2
answers
156
views
Selecting elements of sublists or reshaping a list of lists
I have this list
...
4
votes
2
answers
69
views
Reduction of nested association based on criteria
I have a nested association of the following form:
...
- 113
3
votes
0
answers
113
views
Summation variables aren't recognised as dummy variables
I'm trying to write this expression
in Mathematica, and calculate the following quantity
However, when I tried the following
...
- 229
1
vote
1
answer
81
views
Index an array with condition
I have a list like the following:
list = {{1, 11}, {2, 7}, {4, 2}, {7, 9}, {-2, 1}};
I would like to select those entries whose second elements are greater than 2, ...
- 13
0
votes
0
answers
19
views
Indexing list returned by a function [duplicate]
How do I access elements of a list that is returned by a function?
My function that returns the list is:
b[x_] := (Return[{x, x/2}];)
Then when I try to reference ...
- 165
1
vote
1
answer
48
views
Computing a Transformation then visualizing with TransformedRegion Function
I have some function $\psi$, I compute the transformation $T = \vec{x} - \nabla \psi$. I'd like to visualize the action of $T$ on a square centered at the origin.
The mathematica website shows some ...
- 187
1
vote
0
answers
85
views
Can you create an indexed list of all Wolfram functions within a notebook? [closed]
Can you create a summary list of all Wolfram functions used within a whole notebook? Searched long and hard- no clear documentation found.
6
votes
1
answer
165
views
Undefined Indexed Variable
I searched already a lot about indexed Variables, and it tends to be the most applicable way to use tensor notation. But I am having a hard time to solve for undefined indexed variables:
Here my ...
- 117
2
votes
1
answer
110
views
Plot the indices of the background Matrix instead of the calculated values
I want to create a background 60*100 matrix and insert inside it the calculated values, for example
...
- 119
0
votes
1
answer
67
views
Is it possible to renumber a notebook without rerunning it?
When I prepare a notebook to share with others, I like the numbering of the code cells to start from 0 and to increment predictably to make them more readable, but the only way I know to do this is by ...
- 185
1
vote
1
answer
53
views
How does Mathematica evaluate sums where the upper limit of the index is not an integer?
I am interested in the way Mathematica evaluates sums where the upper limit of the index is not an integer - i.e., sums that are some sense mathematically meaningless. For example:
...
- 2,005
2
votes
2
answers
69
views
How to identify index intervals that contain a value?
I have a really simple question but, sorry, I can't seem to find an elegant solution to other than iterating through. I have a list of indices, and a relative list of values, I would like to extract ...
6
votes
2
answers
184
views
How to create a nested list of variable depth with indexed elements
i want to obtain this definition of a nested list
t = Table[C[i, j], {i, 3}, {j, 3}]
with arbitrary depth,
...
- 503
6
votes
2
answers
328
views
Contracting indices in lists
Using an answer to this question (Working with Dirac Gamma Matrices using FeynCalc - A simple problem), I defined
...
- 73
2
votes
1
answer
224
views
how to add labels of points next to it based on index in ListPlot
I have a list of some points. I plotted each point and its closest surrounding points.
...
- 111
4
votes
1
answer
74
views
Replace pattern with the number of matches so far
I want to replace a n-th pattern match in an expression with n. This is a very simple task, though it appears very hard to find an elegant implementation.
For example, with input
...
- 945
1
vote
1
answer
65
views
Sum index in function collides with input variable
When I enter the following:
Clear["Global`*"]
Func[f_, xx_] := Sum[D[f, xx[[s]]], {s, 1, 2}]
Func[x^2 + y^2, {x, y}]
Func[x^2 + s^2, {x, s}]
The first function ...
- 11
6
votes
4
answers
368
views
How to search within notebooks on Windows 10?
I have a lot of notebooks scattered in my downloads, documents and desktop folder. I have all the required locations on Windows indexing options but if I look at Advanced Options and File Types and nb ...
- 8,377