Questions on filtering or selecting data based on certain criteria. This is to be used with primary tags such as list-manipulation, string-manipulation or signal-processing, with the primary tag indicating the specific use case.

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1
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2answers
48 views

Picking out multiple keys from an array

I have an imported data set that I've used GroupBy on to be organized by specific elements of the sublists within the data. These keys are strings of numbers (in ...
0
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0answers
5 views

What does ℜn mean? [migrated]

I came across the symbol ℜ in the Kalman introduction: http://www.cs.unc.edu/~welch/media/pdf/kalman_intro.pdf x∈ℜm It was used in this context: ...
1
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1answer
68 views

Nested parameter selecting in Manipulate

I have the following code, stripped down from the original to the bare essentials: ...
5
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3answers
70 views

Using select in a nested list [closed]

I have a nested list of the following form ...
0
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0answers
68 views

Pseudorandom selection with double constraints

I have an excel file with data in the format below and I want to extract 30 entries pseudorandomly. There are two constraints: Constraint 1: I need to select 30 of these rows with UPPER LIMITS on ...
3
votes
1answer
68 views

How to implement search patterns and take into account language statistics?

Patterns in Mathematica I struggle some with patterns while trying to extract words out of large texts. Let us say that I have a long text (Strindberg) that we can call ...
3
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3answers
161 views

Question about Nearest [duplicate]

In the following example Nearest finds the nearest values between list1 and list2 and ...
3
votes
1answer
48 views

is there a mode to use Select instead this while loop?

I've a list where a I want to pick up my first element which matches my criteria. This is my work around: ...
5
votes
3answers
186 views

Delete all strings that are prefixes of another string

I have a long list of strings and I'm trying to find a more efficient way of removing those elements that are prefixes of another: ...
0
votes
0answers
30 views

Filtering word data nouns by subfield?

I am making string combinations using WordData and would like to filter all nouns that come from a specific professional specialization. For example, the nouns in ...
3
votes
1answer
78 views

Filtering Background with resonance or Peaks

I have some data, the blue curve which I want to filter out the background to get a flat signal with dips(Idea is to divide signal (except the dips) by the background). The orange curve is my best ...
0
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1answer
43 views

Selecting elements from a list with nulls

I have this list ...
1
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1answer
138 views

Image Filtering in the frequency domain

Here is a good starting to fiter image in the frequency domain lena = ColorSeparate[ImageResize[ExampleData[{"TestImage", "Lena"}],{121,121}]][[1]]; (Create a ...
3
votes
1answer
80 views

How to Operate on a Dynamic Dataset?

I cannot operate on the Dataset I am dynamically filtering. Minimal example follows. ...
0
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2answers
31 views

Finding vertices with a given degree; or, finding indices

I have a graph g and would like to find all the vertices in g with degree n. ...
4
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2answers
135 views

Select non-zero elements [duplicate]

I have a function that generates a list of numbers and variables . e.g. F[w]= {wx, wy, 5, 0} I want to select all non-zero elements i.e. ...
0
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0answers
39 views
3
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2answers
68 views

How to delete list items that contain a non-numeric Part

A sample of the list looks like this: ...
1
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2answers
111 views

Filtering and summing sublists with Cases

I've declared a list: list = {{1, 2}, {2}, {3, 4, 1}, {5, 4}, {3, 3}, {a, b, c}, {e, f}, {g}, {}, {Sin[a], Cos[b]}}; now I've made an rule which add 2 pairs ...
3
votes
0answers
85 views

Filtering in frequency domain

I'm trying to modify a transfer function in the frequency domain by filtering it with a Butterworth filter. For example, let's say my transfer function is of the form : ...
1
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2answers
60 views

Discard Elements of list with given criteria

I have the following list: ...
1
vote
1answer
85 views

How to determine distance of periodic features in measured dataset

I have a list of x- and y-values associated with a measured height (z-values). Part of the list is plotted below. As you can see, there is a periodic arranged structure, namely a cross. Now I would ...
0
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0answers
60 views

Factor Integer function with variable arguments

I'm trying to build a function that gives the highest power of a prime factor of a number. The following works perfectly: ...
2
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3answers
236 views

How to use Select with lists

I am trying to do: Select[minimus[[6]], #1[[2]] < (min[[6]] + emin[[6]]) &] applied to all elements of minimus, ...
3
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4answers
183 views

select elements in a list

I am new in Wolfram Math and I need a help in making a simple program. Let's suppose we have a list: list = {{1, 11}, {2, 7}, {4, 2}, {7, 9}, {-2, 3}, {-1, 10}}; ...
4
votes
1answer
184 views

How to apply by-hand image selection to different images

Mathematica supports image selections by hand, by utilizing the selection tool. I used it to extract relevant data (hundreds of little squares). Now I have a second image of same size, where I want to ...
-1
votes
3answers
80 views

Create table of elements which belongs to specific sets

I would like to produce elements (preferably by Table or For-If commands) that they belong to specific sets. For example I want to write positive integers from 1 to 100 such that they are $2 \pmod 3$, ...
0
votes
1answer
44 views

How to find the lowest power in multi-variable expression?

I am sorry for asking similar question again, I asked How to find the lowest power of variable in expression? and I got wonderful answer, but I have a more question for multi-variable expression. One ...
2
votes
2answers
95 views

How to find the lowest power of variable in expression?

If I have expression like a1/x +a2/x^2 + a3/x^3 I want to return 1/x^3. In general case, ...
5
votes
2answers
95 views

Is there a function that will transform the values of an association while deleting some that match a criteria?

I am looking for something better than Select[Map[f,a],test] As Map will work over the entire association (a) and then Select will work over all of the results. ...
1
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4answers
155 views

Non-rectangular pick of elements of a matrix

How to pick elements of a matrix that are inside a circle centered at the center of the matrix?
1
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2answers
93 views

How to make some mess points to be more smooth?

Background: The question is derive form this post.I have a another thinking about it.Some points in a suface you can give a certain equation but some points you cannot.So I wanna get a method to ...
4
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2answers
140 views

Use Select to filter a dataset's sublists

In the following Dataset, I want to use Select to display only rows, which contain numbers in column ...
0
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0answers
69 views

Engineering spectral densities using filtered white noise

My goal is to create time-spectrum noise signals with spectral densities $S_{xx}(f)$ for pretty much arbitrary spectral densities (think white noise, lorentzian, $1/f$). In finding advice on how to do ...
3
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0answers
63 views

Searching a deeply nested list [closed]

I have a deep nested ragged list. ...
4
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2answers
200 views

Replacing numbers of which you only know certain digits

If I have a list of numbers like this: list = {0.3565127, 0.8656421, 0.231479879, 0.39698787, 0.536987651}, which are all between 0 and 1, each having lots of ...
4
votes
1answer
114 views

Associations complement

So I'd like to complement two associations through shared keys... not the best description, so here's an example: ...
15
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7answers
1k views

How do I delete all items that occur more than once?

DeleteDuplicates works fine but leaves a single copy of the duplicated item. I need to remove all items that occur more than once i.e. {{1,2},{1,2},{3,4}} -> ...
0
votes
1answer
53 views

Filter pattern from a list

I have group elements, that I'd like to condense down according to group rules. Take the modular group. This has generators $S,T$ that satisfy the groups relations $S^2 = I, (ST)^3 = I$. So given a ...
4
votes
2answers
74 views
0
votes
1answer
34 views

Picking some elements of a matrix and generating another matrix [duplicate]

If we have a nested matrix as: start={ {{1, 2, 2, 3}, {1, 1, -2, 1}, {3, 2, 2, -I}, {1, 2, 0, -I}}, {{3, 4, 4, 0}, {1, 1, 4, 1}, {3, 3, 4, -1}, {1, 1, 2, I}} } ...
2
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1answer
37 views

wrong result of an iteration related to replacement and comparing

We have two nested matrix and a code for replacement following an equality as: ...
16
votes
5answers
633 views

Easiest/most efficient way to delete duplicates from one list at the positions of another?

This question is somewhat related to How to efficiently find positions of duplicates? , although I'm interested in something a little bit simpler since I'm not really interested in a list of all the ...
1
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1answer
36 views

Choosing sets from Subsets[list] part 2

Piggybacking off of this question, say if I wanted to exclude sets which weren't the union of elements of the list of lists. For example: ...
6
votes
5answers
159 views

Choosing sets from Subset[list]

Say I have a set, S, and I take Subsets[S] (the power set of S). For example: S={a,b,c} Subsets[S]={{}, {a}, {b}, {c}, {a, b}, {a, c}, {b, c}, {a, b, c}} How can ...
1
vote
0answers
54 views

Select complex mutiple row [closed]

How can I make this select on Mathematica? Is possible?
2
votes
2answers
63 views

Remove an element of a list [duplicate]

I want to check if any element of a list contains Missing["NotAvailable"] If so I want to delete the entire list. If I am correct I need to have some ...
1
vote
1answer
92 views

Manipulating Some Lists in Compile

Consider a list of lists, such as: Z={{1,4,3},{2,1,3},{3,1,4}} Z is an $n \times n$ matrix (here $3 \times 3$) which ...