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.
486
questions
8
votes
4answers
255 views
1
vote
1answer
24 views
Select lists that don't contain a given element (was: elements in a list (all elements should be satisfied)) [duplicate]
I have a big list, for simple, it just like:
...
12
votes
1answer
136 views
Using Select on Dataset with missing keys
I have a very large dataset with about a million entries with up to 75 keys each. Across the whole dataset about half of the keys are blank. In order to reduce filesize, I have used the following ...
2
votes
2answers
84 views
DeleteCases pattern which applies Chop to all elements
In my current macro, I have:
DeleteCases[Chop[FullSimplify[RowReduce[something]]], {0 ..}]
This works fine for both, exact and numeric complex numbers (with ...
0
votes
2answers
28 views
How to select certain numbers to assign a new value and others still keep same
For an array TestA={15,12,5,8,6}, I want to change the value of number greater than 10 into 0, as TestB={0,0,5,8,6}. When using "Select" command, I will lose some numbers.
Thanks.
2
votes
2answers
85 views
How can I implement a simple low pass IIR filter with Mathematica?
I want to design a simple IIR filter with mathematica. For example, consider the filter deigned with this online IIR calculator:
...
8
votes
1answer
130 views
Datasets and Time Values: Filtering and Plotting
After struggling for a few weeks, I have accumulated a few examples of challenging date-related operatations with datasets. Some I have partial solutions; others I cannot yet do. The resources on ...
4
votes
3answers
157 views
1
vote
1answer
40 views
Moving map with non-overlapping window
How can I apply a function to a list with non-overlapping window. E.g. $data = \{x_1, x_2, ...., x_n\}$ and we apply f with window size 2 to get $\{f(x_1,x_2), f(x_3, x_4), ...., f(x_{n-1}. x_n)\}$.
...
6
votes
4answers
333 views
How to delete certain lists from a nested list?
I have a nested list as the following example (want to remove lists with same or incremented elements such as {1,2,3,4,5}, {2,2,2,2,2}, {1,1,1,1,1}):
...
8
votes
4answers
326 views
1
vote
2answers
101 views
How to use FinancialData[] function to filter stocks based on closing price?
I was wondering if it were possible to use the FinancialData function to return a list of stocks based on a price filter, ie. return all NYSE stocks, that had a ...
3
votes
2answers
55 views
Picking elements from a list
That's must be a very trivial question. Suppose we have the simple list
data = {{-1, 0}, {0.2, 0.4}, {4, 0}, {0.3, 0}, {0.2, -0.4}};
Then, is there a quick and ...
1
vote
0answers
33 views
How to filter audio to get best results in correlation?
I am trying to recognise the alphabetical letters by saving some data of records of me and others saying each letter, then comparing a test audio not contained in the data to each letter using the ...
3
votes
3answers
95 views
Find element in a list matching a pattern (using wildcards)
Somehow, I did not manage to find anything related to that.
Suppose, in my Global list of variables, I would like to make a search such that I obtain all the ...
1
vote
1answer
27 views
Selecting only the terms whose exponents add up to a specific number
Suppose I have the expression from a truncated series:
...
4
votes
1answer
89 views
Extended Kalman Filter by hand
While trying to learn a bit about control theory, observers and most importantly, to use Microcontroller Kit in version 12 of MMA, I've stumbled upon the KalmanEstimator.
After reading a bit (and ...
0
votes
1answer
50 views
Delete elements form a list with elements with strings and numbers
I am trying to create a list list2 removing elements from a list list.
The structure of list...
6
votes
2answers
206 views
Find permutation with highest organization number (OEIS A047838)
EDIT: It turns out I misunderstood the definition of "organization number", so the below is incorrect.
However, for every permutation I create with my definition of "organization number", I can show ...
6
votes
4answers
197 views
Take elements from a list based on two criteria
I am trying to take elements from a list of tuples using 2 criteria.
An example of the list is:
list={{-1, -1}, {-1, 1}, {1, 1}, {1, -1}, {1, (1 + I)/Sqrt[2]}}
...
2
votes
1answer
31 views
Select function returns unexpected result [closed]
Recently I notice one fact about the Select function that I do not understand. For example,
...
5
votes
1answer
108 views
DeleteCases using two lists but with partial match?
I searched and tried different solutions on SE but nothing worked.
I have two lists and would like to remove items from list1 that have a PARTIAL match with items ...
1
vote
2answers
82 views
Selecting matrices based on existence of unique column and row of all equal terms
So, I have a list of lists of lists such as the following:
{{{4}},
{{7, 7}, {7, 7}},
{{5, 5}, {6, 6}},
{{2, 1}, {1, 1}}}
Interpreting the elements of this list ...
0
votes
3answers
40 views
Select elements from nested list where one element is largest
I'm trying to speed up the following, but implementing efficient pattern matching isn't intuitive to me yet, even with lots of examples.
I have a list of ((x1,y1,z1), (x2,y2,z2)) pairs, and I want to ...
3
votes
2answers
77 views
Using DeleteCases with a defined function with two arguments as a pattern
I am trying to manipulate some large datasets in Mathematica. I have plotted the data, and I would like to be able to easily remove points from the dataset, and it's fairly easy to identify the x-...
0
votes
1answer
72 views
Produce result faster than “Table[If[…]]”
I would like to generate a list of output satisfying some condition for instance an equation but faster than the following code:
...
4
votes
4answers
181 views
Dropping list elements from nested list after evaluation
I need to create a new list from a nested list but using the evaluation as criteria to drop the elements. For example let's say that that I have the following list:
...
3
votes
2answers
208 views
Eliminate empty elements from a list with a specific pattern
I am really new in this patterns part of Mathematica. Basically what I need to do is eliminate null elements from a list but that has a specific name before the empty element. For example, my list is: ...
0
votes
2answers
69 views
Separating variables in a set of equations
I have a very large set of equations eqs with variables denoted by capital letters like PVA[2], QA[2], etc. and small letters like ica[1,2], tr[2,3] etc. And I have ...
0
votes
0answers
30 views
Export XYZ matrix selecting positive Z data points in three files and keeping the matrix form
The following code saves XYZ points in a separated file but keeping the matrix shape.
...
1
vote
2answers
48 views
Select one among multiple solutions that satisfies a certain condition and 3D Plot it with varying simulation values
My function is as follows:
$$f(x)=ax^5+bx^4+cx^3+dx^2+ex+g=0$$
Since it does not generate an analytical solution, I tried to do a simulation exercise as follows.
Simulation values: $a=-2$, $b=3$, $...
5
votes
1answer
57 views
Select Specific StarData
The help menu for StarData has many examples such as
StarData[EntityClass[
"Star", {EntityProperty["Star", "DistanceFromEarth"] ->
TakeSmallest[10]}]]
...
3
votes
1answer
33 views
How to check format [closed]
I am having troubles with the following data:
slavelist = ResourceData["New Orleans Slave Sales 1856-1861"]
I want to select all slaves with:
...
4
votes
2answers
75 views
Selecting elements of a list based on frequency
Suppose I have a list as follow:
l = {{"a", "b", "c"}, {"a", "b"}, {"a", "d", "b"}, {"a", "c", "e"}};
Now I am going to flatten it and apply ...
4
votes
2answers
156 views
Commonest[] function doesn't actually show commonest elements
I'm using Commonest function on a list with 500000 words to get the 10 most frequent elements. Then by using WordCloud, I found ...
0
votes
1answer
66 views
Solving x'[t]+a*x[t]==0, listing all the solutions, trying to get the value -1x<1 and all corresponding value of a
I am Trying to solve x'[t]+a*x[t]==0,x[0]==1, for x with {t,0,10} using NDSolve.
...
0
votes
0answers
50 views
solving inside for loop and sorting x which are less than 3 and greater than -3 from the list
I give a simple function code here...
Clear[a, x, t];
s = ParametricNDSolve[{x'[t] + a*x[t] == 0, x[0]==1}, x, {t, 0, 100}, {a}]
y = x[1] /. s
y[5] /. s
I ...
0
votes
2answers
54 views
Filter lists by discarding sublists that contain integers different from 0 or 1
Imagine I have a list of the type
Lst = {{1,0,1,1},{4,0,1,1}, {1,1,0,0},{2,1,1,1},{0,0,0,1}}
I want to select only those sublists that only contain elements 0 ...
3
votes
2answers
110 views
How to remove from the data the rows of with fixed number of elements? [closed]
Consider the data which has the form
data = {{x1,y1,z1},{x2,y2,z2,t2},{x3,y4,z4,t4},{x5,y5,z5},...}
How to remove the rows containing three elements from the ...
1
vote
0answers
38 views
How to get a directed graph of size N which is also a connected component?
I need to get graphs of size N, in which the whole graph is a connected component. In particular, I'm working with a Albert-Barabasi distribution, with k=2, and random directed edges.
Right now I'm ...
1
vote
1answer
50 views
How to select the data in a given way?
Consider the data
data = {{x1,y1,z1},{x2,y2,z2},{x3,y3,z3},{x4,y4,z4},{x5,y5,z5},{x6,y6,z6},...}
with N rows.
It can be divided into N/6 sets of 6 rows. I want ...
2
votes
3answers
129 views
Signal Processing [closed]
The image above is the list plot of discrete data I'm working on. Please I need help on how to zero out all the high amplitudes signal from the data. That is all the data in areas circled, I want to ...
2
votes
2answers
108 views
Selecting based on criterion on a single column [duplicate]
I have an array that looks like M = {a, b, c, d}, where a, b, c, d are column vectors. I want to select rows from this array ...
1
vote
0answers
37 views
How to visualize and interactively correct time series data [closed]
I am looking for an efficient method to visualize measured time series data with about 100.000 data points per year, such that eye-catching data points may interactively be tagged as suspicious, e.g. ...
3
votes
0answers
83 views
Select certain term containing some patterns and confusing pattern Alternatives in FreeQ
I am considering a function termsContain[func_,list_] which select in an expression func the terms containing the ones in the ...
5
votes
2answers
182 views
Removing anomalous points from data
I have two sets of 2d-data points which can be transformed in each other by using a certain transformation function.
The problem is that in both data sets there are points which do not have ...
4
votes
2answers
142 views
5
votes
1answer
141 views
Why Cases and Select treat the List differently?
Look at these two examples:
In[1]:=Select[f[i], MatchQ[_f]]
Out[1]:=f[]
In[2]:=Cases[f[i],_f]
Out[2]:={}
It seems that the Select take $f[i]$ as List, but Cases ...
4
votes
2answers
128 views
Select certain terms in an expression
I would like to have a function to select terms containing q[i] terms in expressions, for example, for an expression
a q[i]+b +c q[j]+d
I would like the function ...
3
votes
1answer
165 views
Cleaning away data points which are enveloped within a function
I have some data taken in an experiment which I want to fit and analyse. But before I start fitting function, I want to clean points away in a robust but elegant way.
I first provide some sample data ...
