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Questions tagged [filtering]

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.

3
votes
3answers
96 views

Filter periodical sharp spikes in experimental data

I have experimental data with periodic sharp artefact spikes, which mask the real signal that could be seen as several negative peaks in the first third part on the curve: Is it possible somehow to ...
3
votes
3answers
84 views

How to use “Cases” for isolating terms of a sum in a nice way?

I'd like to isolate some terms with specific patterns within a sum that I called chunk. ...
6
votes
1answer
110 views

Cases, Pattern, Condition [duplicate]

I supposed Cases would do the list produced as example li = RandomSample[Range[100, 999], 30] ...
19
votes
4answers
886 views

How to construct a list of lengths efficiently

Say I have a sorted list of integers RandomInteger[{1, 100000}, 10000] // Sort // Short I want to construct another list whose $m$-th element is the number of ...
0
votes
2answers
30 views

Replace single element of a nested list with multiple elements

I wonder how to replace specific element (even though repeated) within sublists of a nested list with multiple elements while maintaining the list structure. Suppose the following: ...
1
vote
1answer
41 views

Selecting elements using two lists

I made the following list: ...
1
vote
3answers
53 views

Cross checking lists and dropping points that do not belong

I have a list of data that I would like to cross examine with a "correct" list of values and pick out the correct values. For example: ...
4
votes
2answers
88 views

How to use Select for a specific nested list level

I would like to parse every sublist of a nested list and select only those elements that have a certain length, i.e., smaller than 10 elements while maintaining the list structure. Is there any quick ...
5
votes
2answers
148 views

Using DeleteCases to match a string pattern

I am trying to remove all of the elements from a list that contain the characters "err" in that order. I expect the following code to return an empty list: ...
8
votes
2answers
450 views

Ways to speed up Pick

I have a few large arrays (100 times larger than in the example) and I need to re-arrange them. Basically using tests on b and c...
7
votes
2answers
326 views

Deleting duplicates only if they are a certain kind of duplicate

I have a list of tuples like this: {{1,a,b},{1,1,b},{1,a,a},{b,a,1},{b,a,b}} I would like to find a way to delete all those tuples in the list that contain a ...
4
votes
3answers
61 views

Deleting sub-list that contains duplicates

I have a large list of uniform-length lists. What is an efficient way to delete component lists that contain duplicates? For three-item sub-lists, I have used the following code: ...
2
votes
1answer
101 views

DeleteCases does not work with EvenQ? While `Select` works fine [closed]

EvenQ[FromDigits /@ Tuples[{2, 3, 5, 7}, 5]] Works fine. But ...
1
vote
2answers
34 views

Select equations with RHS!=0 from a list

I need to select from a list containing equations those having RHS not zero ...
0
votes
1answer
44 views

How to automatically select solutions from a set of solutions given by Solve?

I have a function of trigonometric functions which must be equated to zero in order to obtain the appropriate results. This is done in the following fashion: ...
0
votes
1answer
55 views

How to replace a special arrow and row in a matrix with a symbol and drop it? [closed]

I need to do a iteration, if condition[i] is true, I want to drop i row and i column in the matrix A. To keep the index of A unchanged, I think I should replace i row and i column as zero or other ...
2
votes
1answer
39 views

Filter rows in nested Association / Dataset using Select

The Dataset I am working with has the following nested structure. ...
2
votes
1answer
49 views

Select elements in a list of tuples of quaternions that satisfy a condition

I defined 24 quaternions using the Quaternions package and i create the list of all possible 4-tuples using ListQuad = Tuples[ListQuaternions, 4] where ...
7
votes
3answers
175 views

Finding items satisfying a condition in a list using patterns

Why the following command Cases[{1, 2, 6, 3, 4, 8, 5}, {x_, y_, z_} /; (y > Max[x, z]):>y] doesn't return the y values that are greater than their ...
12
votes
10answers
1k views

Given a list of integers, find the largest sum of a contiguous subsequence

Given a list of integers, find the largest sum of a contiguous sub-sequence. {1, 2, 3, 4, 5, -1, 7, -4, -2} (* 21 *) And print the sub-array which is ...
1
vote
1answer
33 views

how to filter a table based on predicates involving column values

I would like to select a small subset of rows of a table based on a predicate involving multiple columns. Here's a small example of what I want using For[]: ...
2
votes
1answer
29 views

Why does N result in some inconsistency in this context?

In the following, why does N not produce the expected decimal output, while Round does? ...
13
votes
2answers
359 views

How to build a list of elements satisfying a certain property without building a list of all elements first?

Is there a way to directly build a list of elements that satisfy a certain property? More precisely, I am looking for a function IncludeIf (this is a placeholder ...
1
vote
4answers
72 views

How to extract certain rows satisfying a condition?

I have three columns - P1,P2,M and 411935 rows. I want to extract only those rows which satisfy P1>=P2>=0.25*M. How can I do it?
1
vote
1answer
53 views

How to select terms which contain certain letters?

I would like to select the term Subscript[Cos\[CapitalDelta], Subscript[p, B]] of expression ...
6
votes
3answers
249 views

Remove elements from deep nested list

I have a list like this. How do I traverse the sublists to remove all the 1.'s but leaving the structure intact? I have attempted with Drop[list, {1}] but this ...
0
votes
0answers
45 views

Butterworth single pole, 5 Hz cut-off frequency on accelerometer data for single axis

I have read other posts here on using the Butterworth filter in Mathematica, however, I am having a hard time understanding the chain of functions and their parameters as applied to my case, and I am ...
7
votes
4answers
255 views

Deleting list elements by comparing to another list

I have two lists as follow. The first is p={{"j","d","x"},{"d","k","z"}} and the second one is: ...
5
votes
3answers
137 views

Select the cases by comparing the second elements of the list

Suppose I have a list: l={{1,4},{2,4},{3,5},{4,6},{5,3},{6,2}} How can I select the elements of the list in the second element is decreasing and first element of ...
1
vote
1answer
49 views

Choosing data from list and plot [duplicate]

I have a data set like below: Angle={5.48575, -0.669213, 45.9832, 8.63878, -16.8777, 50.022, -41.8882, -45.956, 28.3005, 35.8234} Now want to select the ...
2
votes
1answer
62 views

Select the right XMLelement

I scrape data from a public website about houses for rent. All pages have the same structure. But the pages can differ in the amount of information. Below I give two examples: page/house 1: ...
7
votes
2answers
197 views

Select UPPER CASE list items with spaces and punctuation

I have a sample list that includes people's names in Title Case, and their companies in UPPER CASE. ...
3
votes
2answers
79 views

How to filter-out edges in a HighlightGraph[] visualization based on VertexCoordinates[]?

I need to visualize a graph spatially, and I'm simply using: HighlightGraph[ConnectedGraphComponents[]] and the known coordinates of the graph's nodes. I really ...
7
votes
4answers
295 views

How to remove “extra” edges from a multigraph?

I programmatically generate many large undirected graphs. Sometimes these graphs are multigraphs, that is, they contain more than one edge between a pair of nodes. I've tried to delete the "extra" ...
2
votes
4answers
222 views

Smoothing noisy data

I have this data shown in picture 1 below and I want to filter it. I tried some filters but I couldn't get good results. seems that I didn't choose the best parameters for it. I want to smooth my ...
3
votes
1answer
88 views

Applying TemporalData to array before filtering gives wrong results

I had a task of filtering data with various timestamps on it, and proceeded as instructed. The first option was to use TimeSeries which works fine but somewhat slow, and the second one TemporalData ...
11
votes
1answer
132 views

How to delete lists that contain sublists of different sizes?

I hope to have your help, if I have listp = Permutations[Range[7]]; With the following functions, I delete the lists that contain ...
8
votes
1answer
234 views

Sample rate severely influences quality of ButterworthFilterModel?

I've hesitated for a while about whether this should be posted to dsp.SE or not, but still decide to discuss it here. Today I was playing with ...
2
votes
1answer
91 views

Butterworthfilter highpass/bandpass

this should be a fairly straightforward question since Mathematica has included functionality to filter data. Nevertheless, I am not being successful to solve the problem. Following the proposed ...
5
votes
4answers
458 views

How to increase the speed of DeleteDuplicates on some selected columns?

I have a data1 with 4 columns and would like to remove the duplications by looking at the first 3 columns. Thus I used below code:- ...
4
votes
1answer
58 views

How to select only some values of an association based on some criteria

Here is the association I have: assc = {"abc" -> 2.456, "efg" -> 3.652, "_final" -> 6.108} I need to remove all key-value pairs where keys start with '_'...
0
votes
2answers
66 views

eliminate product terms in equation [duplicate]

I would like to eliminate all terms that contain the product of dxy, dwz, and dxz, i.e. the final result should read as dxy +b dwz+ c dxz. Thanks in advance for any hint. ...
3
votes
2answers
99 views

Need help charting school shootings by year and number of victims

For my school project I've decided to take some data from Wolfram. I have the dataset from Data Repository, and I want to create three BarCharts. The first one shows the highest number of fatalities. ...
4
votes
2answers
73 views

Deleting elements from a list based on their relative position to one another

I have a data set where I often get pairs of spikes that occur randomly but the pair is always separated within $n$ places of each other. I.e. the spacing between the pairs, in index, is always ...
4
votes
3answers
173 views

Keep only rules that replace integers with other integers

Let's say I have a list of replacement rules: List1 = {2 -> 3, b -> 5.5, 6.57 -> 2, 3 -> 4.5, 1 -> -1, 0.03 -> 0.5, 9 -> a} The desired ...
3
votes
1answer
64 views

Deletion of list elements containing a string character

I have a list: lis = {"ab","a-1","1-20"} from which I need to delete elements of lis that has (only) digits on both sides of the hyphen, in each element that ...
1
vote
2answers
79 views

Selecting elements in nested list

I want to compare elements in a list that looks like this ...
4
votes
4answers
134 views

delete an element list recursively

I have a list, say {10,9,8,7,2,3,5,4,3,2,1} What I want to achieve is to delete the elements that are not in decreasing order recursively. Namely, the output ...
1
vote
0answers
57 views

Filtering list using function values [closed]

I have a list (Basis) of size $2^{21}$, and a binary function $A$ defined on it (only outputs 0 or 1). I want to filter out the items from Basis that $A$ sends to 1. I was able to find the size of the ...
0
votes
2answers
63 views

Remove a term which includes a defined variable from an equation

Is it possible to remove a term which includes a defined variable from an equation? my equation is something like: ...