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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23 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 ...
2
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1answer
21 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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0answers
22 views

Savgol Filter Smoothing [on hold]

How can I improve my savgol filter? I have it currently set at a window length of 5, and a polynomial order of 2, but I want to increase the smoothing ability. Is there any way that I can do so?
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2answers
29 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
126 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. ...
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0answers
33 views
3
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2answers
66 views

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

A sample of the list looks like this: ...
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2answers
105 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
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0answers
78 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
57 views

Discard Elements of list with given criteria

I have the following list: ...
1
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1answer
82 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 ...
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0answers
57 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
233 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
votes
4answers
176 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
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1answer
168 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 ...
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3answers
76 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
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1answer
37 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
90 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
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2answers
94 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
144 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
92 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
132 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 ...
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0answers
61 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
59 views

Searching a deeply nested list [closed]

I have a deep nested ragged list. ...
4
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2answers
199 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
112 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
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1answer
52 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
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2answers
72 views
0
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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
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5answers
626 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
157 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
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0answers
54 views

Select complex mutiple row [closed]

How can I make this select on Mathematica? Is possible?
2
votes
2answers
58 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
91 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 ...
7
votes
2answers
148 views

Get association element that has a parameter

Say I have an Association of the form: assoc = <|first->"abc", second[param]->"xyz"|> Now to access ...
6
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5answers
144 views

Simple Enumeration of Coin Tosses

How do I enumerate a sample space with up to 6 coin tosses where 4 Heads ensures a win. For e.g {HHHH},{HTHHH},{TTHHHH},{HTTHHH} etc.I tried the following but I do not know how to do a variable length ...
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0answers
39 views

select year 2014 from an object [closed]

could you help me to filter the year 2014 from the following object: data={{2013.09.17, 60.},{2013.10.07, 100.}, ...... } Basically I just want to select one ...
6
votes
3answers
74 views

Using Select on a 2d table with a criteria that accepts 3 parameters

I have a table sets := Table[{i, j, k}, {i, 1, 10}, {j, 1, 10}, {k, 1, 10}] and I want to use a function that accepts three parameters and returns a boolean, as ...
2
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3answers
154 views

select from a list of disks

I have the following list of centers of disks. ...
1
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1answer
40 views
2
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0answers
44 views

Performance of different Count patterns

The two pieces of code below are functionally equivalent, and I would have expected similar performance. (The only difference between the two is the form of the pattern used.) But the second piece of ...
4
votes
6answers
427 views

Remove the odd element from a list

I have a list, which contains more lists with elements, see example {{1, 1, 1, 1, 2}, {2, 2, 2, 2, 3}, {3, 3, 3, 4, 3}} I want to remove num 2 from the first list ...
4
votes
2answers
149 views

With “named row” nested Datasets: How to Select or Filter rows by row key with criteria from another Dataset?

After some calculations and grouping I have a Dataset similar to the following form: ...
7
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3answers
228 views

Deleting any list that contains a negative number

We had another nice question in a student activity today. The increasing sequence of positive integers $a_1,a_2,a_3,\ldots$ has the property that $$ a_{n+2}=a_n+a_{n+1} \text{ for all } n\ge 1. $$ ...
1
vote
2answers
195 views

How to speed up a For-loop [closed]

My code is the following: ...