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

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3answers
115 views
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1answer
115 views

How to define Similarity Rules?

I have a question about Mathematica's SimilarityRules defining (for e.g. SequenceAlignment function). So help centre clearly ...
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1answer
180 views

Searching a string that may contain Null

I have an array of triplets that can be approximated by the following code: ...
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2answers
290 views

Collect pattern (Log's)

Is it possible to apply "Collect" command (to put Log's in particular combination) to factor out (pattern) a particular form from the full expression. For example, consider the following expression: ...
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2answers
267 views

Deep Pattern matching with repeating arguments

I have a function that accepts a single argument that is described by the following grammar: ...
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2answers
235 views

A function that only evaluates on lists of pairs [duplicate]

Possible Duplicate: Why doesn’t PatternTest work with Composition? I'd like my function to only evaluate when the argument is a list of pairs. It seems like ...
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1answer
55 views

Count and NMinimize don't seem to work together

Initially I write down a 2x2 unitary (Uni) , make a tensor product 4 times (LocalUni) and apply it to an initial numerical matrix Rho, to obtain RhoLU, that depends on 12 parameters. This is my code: ...
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1answer
67 views

How to bound a recursive Derivative definition?

I need to convert derivatives of g[x,v] wrt v into derivatives wrt x using this relation: $$\frac{dg[x,v]}{dv}=\frac{1}{2}\frac{d^{2}g}{dx^{2}}+\frac{1}{2}\left(\frac{dg}{dx}\right)^{2}$$ This code ...
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1answer
79 views

How to write a pattern that matches all functions

What is the correct way to match a function in an expression in the way that Cases[Sin[x] Cos[x], _Sin | _Cos, {0, Infinity}] matches ...
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1answer
45 views

Matching x,y,z,2

I have a list of integers; I would like to replace anything of the form $x,y,z,2$ in such a list with $x+1, y+1, 0, 0$. The problem is that the $2$ may appear at the front, or in the first three ...
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2answers
186 views

dropping a row with at least one value larger than a particular value

So for instance I have M X N table. I want to drop any row which has an element larger than, say, one in the second or the third column. I guess I have to do some sort of pattern matching. But not ...
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1answer
37 views

Please explain this pattern/Message related issue and help with finding workaround

I attempted to clean up my code and also add messages to functions if they are called with wrong arguments. This introduced some error which I tracked down to the following: ...
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1answer
64 views

How to use PadeApproximant with a defined Derivative?

I need to generate a Pade approximant expansion in v of the following: $$g(x,v)\equiv ...
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1answer
57 views

Emulating Case Pattern replacement

As most regular users, I have developed utility functions complementing the Wolfram language for frequent tasks. In particular, I have variations on Cases (see ...
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1answer
104 views

Dealing Repeated pattern in StringReplace

A problem about StringReplace When I'm running into this problem possible [bug] ...
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1answer
38 views

How do I match all the subscripted terms in Times?

Suppose I have an expression: $W = A_{i,p,q...}\,\, a_ia_ja_ka_l...$, where $A_{i,p,q...}$ is an expression that does not depend on $a$, the indexes $i,j,k,l,p,q...$ are integers and all the integers ...
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2answers
71 views

How do I format expressions so that replacement rules correctly apply to exponents? [duplicate]

I have a series of rules that I would like to apply to a series of expressions with variables, but cannot get Mathematica to correctly recognize that these rules should apply when my variables have ...
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1answer
94 views

Matching variables with Subscripts yielding True and False

I am trying match variables with subscripts just returning true or false depending if pattern is matched. My try is to use Cases. However the following does not ...
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1answer
91 views

Substitute complex functions into complicated polynomials

Mathematica has some strange way of sorting terms. It seems that it is using a canonical sort on expressions, e.g. $\mathbb{i} \sin[x] \cos[y] \cos[z]$ is returned as $\mathbb{i} \cos[y] \cos[z] ...
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1answer
227 views

Do any users know of methods to capture Twitter feeds and subject them to analysis? [duplicate]

I would like to use the output of about 300 Twitter sources and would probably collect 30 minutes of tweets at a time and subject each collection to analysis; ideally this process would be automatic ...
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0answers
89 views

Need help interpreting a small block of code [on hold]

I have recently "inherited" some Mathematica scripts which I need to interpret to write in some other languages (Maple and C++). I have never used Mathematica before so I have been learning on the ...
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0answers
44 views

Pattern placeholder for zero or more matching items in list [closed]

I'm working through the exercises in Stephen Wolfram's book "An Elementary Introduction to the Wolfram Language." In Chapter 32 on "Patterns", Exercise 32.1 is "Find lists beginning with 1 and ending ...
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0answers
57 views

Good coding for integral substituions

This question is aimed at improving both my coding and my understanding of MMa's capabilities. A lot of my code is still hacks and workarounds for things I don't know how to do properly. I want to ...
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0answers
68 views

Unexpected result when trying to match against the arguments of Times

Consider the following question: ...
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0answers
57 views

Why has FreeQ a quadratic complexity with high depth?

I am a little puzzled by the following test: ...
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0answers
39 views

What does __Rule do in Mathematica? [closed]

What does __Rule do in mathematica? I understand the __ is used for any repeated expression, but why is the Rule appended at the end? For example: Import nested JSON file Thanks!
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0answers
109 views

How to Pattern Match complicated patterns? [closed]

How can I get the output expressed in terms of p1 and p2 instead of exponentials? ...
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2answers
96 views

Is there a way to search for Arithmetic Progressions in a list?

If you have a list of integers is there a way of searching that list to see if there is a trend of Ax+B in the list? Not using all of the numbers, just seeing what trends like that are embedded in a ...
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0answers
37 views
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1answer
59 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): ...
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2answers
184 views

Pattern Matching in Lists

I have a UN voting dataset – taken from a CSV file – where each row is in following format: ...
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1answer
56 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: ...
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0answers
202 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, ...
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0answers
103 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 ...
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0answers
50 views

How to pattern match an association? [duplicate]

I have the following: Clear[a, b]; a = {{1, 2, 3}, {4, 2, 5}, {6, 7, 8}}; b = GroupBy[a, #[[2]] &]; b whose output is: ...
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0answers
46 views

Placement of pattern matching rules in functions [duplicate]

Is there any difference at all between f[x_Integer /; x >= 0] := x + 1; f[x_Integer] := x - 1; f[x_] := Null; and ...
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0answers
59 views

Hashing by Equals instead of SameQ

I have some numerical code involving complex numbers representing points on a plane. Some of these are equal but not identical, ie ...
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0answers
80 views

Function behavior based on Head

I'm figuring how to implement a function behavior based on the Head of its argument. I mean ...
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0answers
43 views

Matching Root[…] objects with patterns, unexpected hidden argument

I needed to write patterns that could distinguish between arbitrary-function and polynomial forms of Root objects, for example, ...
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0answers
37 views

Pattern matching list elements in pure functions [duplicate]

Pattern matching here is a functional programming term, but it might be called differently in Mathematica, I'm not sure. It is possible to match the elements of the list in a regular function ...
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1answer
224 views

Functions that operate on symbolic matrices?

I'd like to write functions that operate on symbolic matrices, and do nothing when fed anything else. ...
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4answers
139 views

Cases vs Select, Pattern vs Pure function [duplicate]

What is the difference between having Cases with selection condition presented by pattern and a with pure function as condition? ...
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3answers
72 views

ReplaceRepeated made a single replacement where I expected multiple replacements to be made

This seems like a very simple action: {a, b, c, d, e, f} //. {r___, x_, y___} :> {r, 1, y} but it replaces only the first element giving ...
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4answers
140 views

How to trim the zeros from the right of a list? [duplicate]

I need to remove the zeros from the right of an integer list up to the first non-zero element. Such as {0,1,0,0,2,0,0}->{0,1,0,0,2}. Padding zeros can be simply ...
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2answers
64 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 ...
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1answer
119 views

Match a variable name pattern [duplicate]

I have a list of variables: {RBI,RCD,ASD,FGH} I want to select only those whose name starts with R. Using the pattern Rx_ ...
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2answers
88 views

Match groups in regular expressions

I'm trying to understand Mathematica's pattern matching in strings, but I have some doubts. 99% of the time I need to a) check if a match occurs and b) retrieve the matched patterns. I come from ...
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3answers
75 views

How to create a general expression for an integer derivative?

I need MMa to return a general expression for the jth derivative wrt v of v^n. This didn't work: ...
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1answer
157 views

Extracting graphics primitives from a Graphics expression with ReplaceAll

If we have a graphics object, plt = Plot[Sin[x], {x, 0, Pi}] and we need to retrieve the discrete point data from it. This can be easily done by using ...
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1answer
35 views

How to pick max/mins of elements that match patterns?

I have a list of complicated expressions that involve indexed coefficients. For example: expr={m[5],c[3]*m[1]^2+m[2],Sqrt[m[2]+3*m[3]*c[8],foo[m[3]*m[5]]}; How ...