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Newest 'pattern-matching' Questions - Mathematica Stack Exchange
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Learn more about TeamsQuestions tagged [pattern-matching]
Questions on expression testing and manipulation through pattern matching and constructing efficient patterns.
1,603 questions
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7
votes
1
answer
418
views
Why `MatchQ[ 3 + x, _ + _ ]` return `False`?
Consider
MatchQ[ 3 + x, _ + _ ]
It returns False. Why?
After some research, I concluded that it's due to the ...
2
votes
1
answer
101
views
Difference in pattern matching before & after Expand
The goal is to substitute m2/m1 in expr with k. Code1 does not match the pattern, but if it is pre-processed with Expand like in code2, it matches the pattern. Could I know why there is this ...
2
votes
0
answers
81
views
Unexpected result with Position using pattern
I use Mathematica 12 and have the following code
t1 = {1, 2, 3.1, 4, 5, 6, 7.1}
Position[t1, x_ /; Not[IntegerQ[x]]]
which gives me
...
- 3,120
0
votes
1
answer
110
views
Generalizing a function to ignore Missing
When the arguments contains Missing[] at the start of the data I find myself doing /.Missing->Nothing to the arguments and <...
2
votes
3
answers
154
views
Removing unmatched elements from nested list after ReplaceAll
I'm doing some heavy symbolic calculations and for preliminary simple tests I need to replace all coefficients except some choosings, e.g.:
...
5
votes
2
answers
155
views
Quickly checking Missing[] is only at the start of a list
I am working with Tabular data and I want to check if Missing[] is only the first contiguous part of list. e.g.:
...
0
votes
2
answers
100
views
Why does a replacement rule fail for a custom defined function but works for a generic symbol?
I'm pretty new to Mathematica and I have a question about how to deal with replacement rules in presence of function definitions.
Basically I want to implement a mean/covariance calculator, in the ...
4
votes
4
answers
261
views
How to Determine Whether Number or Symbol
I want to implement a function looking like this:
func1[func2[k],m,n]
If m and n are ...
3
votes
4
answers
703
views
Why cannot "a" be 0 in this pattern matching?
Why does the pattern matching not work if k is 0 (either explicitly or implicitly)? Is there any method to make it work?
...
1
vote
4
answers
210
views
Any More Flexible Pattern Matching?
I tried to define a simple function with pattern matching:
F[(n_ - k)*T[n_ + 1 - k]/m_] := k*n/m
But when I run ...
1
vote
1
answer
97
views
Why Cannot I Apply the Replace Rule Here?
I want to replace
$p_\_\sum_{i=1}^{m_\_}Log[x[i]]^{b_\_} x[i]^{a_\_}$ with $p*T[a,b,m]$, but it doesn't work. Can anyone give me a help? Thanks in advance!
Codes:
...
4
votes
2
answers
296
views
How to set to 0 all terms in a matrix which contain a minus, revisited
The previous question How to set to 0 all terms in a matrix which contain a minus seems to have a wrong answer. For the matrix
...
0
votes
1
answer
65
views
Counting matching elements in two lists or vectors, excluding blank or Null elements
I need some help with a pattern-matching problem. I want to count the number of matching elements in two lists (or vectors) of equal length. To be concrete, consider a multiple-choice test with 5 ...
2
votes
2
answers
193
views
Partial derivative of function with restricted pattern like _List doesn't evaluate
I am having trouble where Mathematica won't evaluate my partial derivatives. I have the function below.
...
1
vote
1
answer
109
views
Attribute based pre-processing of arguments
I work with hashes that can be related to various data structures.
I find it convenient to have my functions work either when a hash argument is provided or when the required data structure is ...
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