Questions on expression testing and manipulation through pattern matching and constructing efficient patterns.

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0
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2answers
52 views

FilterRules with pattern for name [duplicate]

I have a list of rules and I want to filter it using a pattern for the initial string representing the name of the rule. So that in the example below it filters linearBool even if it is called ...
2
votes
1answer
118 views

Odd behavior matching powers of pi

I have a long list of generated values from which I want to remove "weird" ones like Sin[Sin[1]] and Pi^2/4. However, trying to ...
4
votes
2answers
112 views

Output function control and manipulation for efficient computation [closed]

I have taken note of a similar post related to modifying function parameters. I tried to adapt Kuba's solution to this post but I can't get it to work. I will illustrate my problem using a similar ...
3
votes
1answer
156 views

Pattern matching multiple symbols names and powers

Seemingly a relatively simple problem, I can't seem to find a solution... I want to build a pattern that will match any symbol whose name starts with V, and is elevated at any power. Something on the ...
1
vote
1answer
53 views

How to modify the output result of an evaluation

For ease of notation, I have defined a function, $f$, that defines the permutation of Bosonic particles such that it has the following properties (the form of $f$ is irrelavent for this question): ...
7
votes
3answers
238 views

Why these ways of defining a function with variable number of arguments fail?

First: I know about the correct way to define a function with variable number of arguments: Clear[f] f[s__] := Plus[s] f[1, 2, 3, 4] (* 10 *) BUT I ...
0
votes
2answers
66 views

Keep exponents separately

I have the following expressions $g^{ab+cd+...}$ or in the full form Power[g,Plus[Times[a,b],Times[c,d],...]] How to convert this expression into ...
4
votes
3answers
98 views

Extracting subscripts and superscripts

Suppose I have several types of expressions (in some random order) of the form Power[Subscript[g, a], μ] which is $g_a{}^\mu$ ...
10
votes
1answer
373 views

How to visualize pattern matching process?

I want a function that does the same job like ReplaceRepeated, and can make the matching process visible. I searched the Internet but didn't find any existing code ...
3
votes
4answers
235 views

How to search for patterns to find the positions of prime numbers

I have a summation which yields a prime number at each location there is a 2, and I do not know how to search for the 2's. ...
7
votes
5answers
546 views

Calculating weird numbers

A weird number is a number such that the sum of the proper divisors (divisors including 1 but not itself) of the number is greater than the number, but no subset of these divisors sums to to ...
4
votes
3answers
185 views

How can I improve NumberString?

I would like to test strings to see if they represent numbers. This should include number representations with precision marks and scientific notation. NumberString ...
10
votes
2answers
507 views

Is there a way to identify a symbolic fraction?

Is there a way to use Head to detect a symbolic fraction? In particular I find, Head[a/b] Head[1/5] Times Rational ...
4
votes
4answers
164 views

Cases with Alternatives failed

Consider this list of rules rules = {a -> 1, b -> 2, c -> 3} I'd like to fish some of the rules out of such a list using ...
6
votes
5answers
238 views

Counting subsequences (i.e., patterns) within a list?

I would like to count the number of subsequences in list. Say I have data given by: data = {1, 1, 1, 2, 1, 2, 2, 2, 1, 2, 1}; I would like to count the number ...
3
votes
4answers
112 views
2
votes
3answers
97 views

Testing for a vector of reals [closed]

Suppose I define: RealVector[expr_]:=VectorQ[expr,NumberQ[#]&&Head[#]===Real)]; Then: ...
1
vote
1answer
69 views

How to use a list of rules as a data set

I have a file of models that I have saved that I want to be able to call in another program to be solved with NDSolve. Can I use ...
0
votes
1answer
120 views

Replacement of terms/Pattern matching involving products of derivatives of a function

In delving into Ramanujan summation, I'm trying to get a hold of the relations of the form $$\sum_{n=0}^\infty f(n)=\dfrac{h\frac{d}{dx}}{{\mathrm{e}^{h\frac{d}{dx}}}-1}\int_{0}^\infty ...
14
votes
1answer
123 views

Unexpected pattern matching behaviour: PatternSequence vs. Optional

fixed in 10.1 (windows) Consider the following pattern-matching expressions: ...
6
votes
5answers
228 views
0
votes
0answers
50 views

“Meta-matching” patterns [duplicate]

The title refers to the general problem of writing patterns to match pattern-containing expressions (hence "meta-match"). Here's an example. In the following rules ...
2
votes
1answer
54 views

What's the pattern that will match a head anywhere in an expression

I'm looking for the pattern patt[head] that will match any expression expr in which head occurs as a head anywhere within expr. ...
3
votes
2answers
147 views

Replace expression, but only “outside” of a function [duplicate]

I have a horrid expression, which is basically a sum of exponents with coefficients. Here's a taste: What I want to do is to replace ks with another expression, ...
2
votes
2answers
131 views

Problem using Position applied on matrix with Infinity elements

Am I doing something wrong here? ...
12
votes
1answer
257 views

Orderless pattern matching

The MMA docs state that "In matching patterns with Orderless functions, all possible orders of arguments are tried". Why then does the following not work? ...
0
votes
2answers
48 views

Matching exponents using Cases[]

I have a question regarding pattern matching. Can anyone explain the results i get ? Cases[Table[x^n, {n, 1, 10}], a_^1] Which gives the following result. {x, ...
1
vote
2answers
175 views

Pattern Matching in Lists

I have a UN voting dataset – taken from a CSV file – where each row is in following format: ...
1
vote
2answers
123 views

Pattern Match and Replace Expression involving Pure Function

Let's say I have an expression that in held form contains a pointer to a function. expr = Hold[2*{"FUNCTION1"} + 5]; ...
2
votes
1answer
41 views

Default value behaves differently when used in Function and when used with Cases

Consider this example: Cases[{4, x, 5 a , 6 x}, x_.*a_ :> x] (*{1, 1, 5, 6}*) It is clear that the _. took 1 as a ...
7
votes
1answer
147 views

LetterCharacter for Cyrillic symbols

Why does the code StringMatchQ["ы", LetterCharacter] return False? Probably because: ...
3
votes
2answers
89 views

Power[__] Pattern works like Level

I came across this case: ...
2
votes
0answers
55 views

pattern matching and applying a function, not working as expected [duplicate]

Consider the following code G[x, y] /. a_[b__] -> Total[a @@@ Permutations[List[b]]] I expect it to give G[x, y]+G[y,x] ...
0
votes
1answer
80 views

How to ensure efficient order of operations for rules, slots, substitutions?

I need to calculate several functionals Q[[t]] of a pdf f[x]. ...
2
votes
1answer
123 views

How to use slots and patterns to reduce repetitive calculation?

This is kind of complicated... How can we make MMa calculate values of a function before doing multiple pattern or slot substitutions? Answers to similar questions didn't cover the case where the ...
10
votes
2answers
173 views

Unexpected result from StringReplace

The following works as expected. StringReplace["xxxyxz", "x" ~~ _ -> "ww"] "wwwwww" And so does this. ...
2
votes
0answers
118 views

Is this a bug in NCAlgebra library?

In course of my work with NCAlgebra package for Mathematica, http://math.ucsd.edu/~ncalg/ , I encountered unexpected behavior of replacements. I am using ...
1
vote
1answer
52 views

Pattern matching functions of variables

I am trying work with a general operator z[] and later plug in candidate forms for z[]. But pattern matching turns the inside z[] into a constant and can no longer perform operations on it: ...
2
votes
3answers
253 views

Mathematica won't plot the a function that is solved from NDSolve

I have used NDSolve to solve for a function (an angle of a triple pendulum), and now I wish to plot the derivative of that function (the angular velocity). ...
1
vote
1answer
154 views

Finding the index of (x,y) pairs in a list

I have a large list of $(x,y)$ pairs, and I want to find the index of a particular pair in order to extract some data from another array. By way of an example, ...
5
votes
3answers
503 views

Camel hump string split

Given System names of 2 or more characters: systemNames = Names["System`*"] // Select[StringLength[#] > 1 &] ; Is ...
4
votes
1answer
71 views

How to define patterns to filter lists of replacement rules? [closed]

I have a list of replacement rules like list˘of˘replacement˘rules = {a -> 1, b -> 2, c -> 3} and I want to filter all the elements where ‘b’ is replaced ...
1
vote
0answers
162 views

Crosscorrelation for nonperiodic signals

I want to detect patterns (of an absorption spectrum which is nonperiodic) with Mathematica automaticly. I have found CorrelationFuncion but as far as I understand, ...
3
votes
3answers
246 views

String pattern defined by number of characters

I want to extract non-overlapping substrings from strings with only four possible characters a,b,c,d. These strings will always have equally many "a" and "d" characters. The substrings x I want satisy ...
2
votes
1answer
111 views

Deleting empty cells and selecting cells matching a pattern

Is there any way for me to automatically select all cells that are completely empty? You know, those cells that you create but end up cutting what's in them and paste it somewhere else, so after a ...
2
votes
1answer
38 views

Linear function on strings using UpValues

I have two functions Sup and Sdown that take a string of letters with allowed characters ...
1
vote
0answers
55 views

Find d'Alembertian in the output and convert into Einstein summation convention form [closed]

How can I identify the d'Alembertian in this expression: $ -\frac{1}{c^2}V^{(1,0,0,0)}[t,x,y,z] + V^{(0,1,0,0)}[t,x,y,z]+V^{(0,0,1,0)}[t,x,y,z]+V^{(0,0,0,1)}[t,x,y,z]$ and convert it into the ...
7
votes
3answers
147 views

Pattern matching: Times[a_] vs Times[a__]

I don't understand why MatchQ[ HoldComplete[Times[3, 2, 2]], HoldComplete[Times[a_]] ] is returning True. I thought that ...
1
vote
0answers
88 views

Symbolic and numeric calculations (and plots) simultanuosly

I use Mathematica to do a bunch of symbolic calculations (integrals, ...). This is good because I found that sometimes, if I plug in numeric values, Mathematica takes much longer. However, sometimes ...