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

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3
votes
2answers
102 views

Pattern match any member of a Context

Let's say I have four functions: x, y, X`x, and X`y. ...
3
votes
1answer
93 views

Custom operators; custom pattern matching with pure functions

What I'm trying to achieve in Mathematica is the creation of a binary operator whose operands are both pure functions over the natural numbers. The result of the operator should be another pure ...
3
votes
1answer
82 views

How to localize symbols on the right-hand side of Rule when using ReplaceAll?

I am frustrated by the following: {1, 2, 3.0} /. a_Integer -> a + 1 The a on the left side of the arrow is localized and ...
3
votes
2answers
175 views

Finding similar expressions in list

I have a function that returns to me lists of expressions, like: ...
3
votes
1answer
109 views

Inheritance in Mathematica using pattern matching on UpValues

Edit: I think in my original post, I missed emphasizing the main point. This is mainly a pattern matching question. If you're interested in the 'why' of this question, please read the original post ...
3
votes
1answer
90 views

Use of StringExpression as argument

Is it possible to use a StringExpression as a pattern for an argument? I.E. something like foo[chars__~~ WordCharacter.. ~~ num:NumberString] := {chars, num}; At ...
3
votes
3answers
176 views

Write a function using pattern test to test whether the input is polynomial and print error message if not

I am doing this which is supposed to be an easy problem and which I think my code should be correct but for some reasons it is not working. May anyone help correcting my mistakes? How should I write ...
3
votes
1answer
123 views

How to make a pattern to change x^(2/y) to (x^2)^(1/y) for any x and y?

This might have been asked before. Please let me know if it is. I was looking at an interesting Mathematica question in students forum and trying to solve it, and a chance to learn more about ...
3
votes
1answer
81 views

Why does pattern test not work in this case to restrict the function parameters?

I was looking at this Q&A about using pattern test (pattern_?test) vs pattern condition (pattern_/;cond) and came across ...
3
votes
2answers
116 views

truncating terms in symbolic expression basing on their values

I need to simplify big symbolic solution of equations system by truncating terms that are orders of magnitude less then others in subexpressions like a + b. The solution is big fraction with sum of ...
3
votes
1answer
154 views

Problem with | operator in pattern matching

My first question here as I only got into Mathematica programming recently. Basically I have a large symbolic algebraic expression where I know certain variables with head pε appear with degree 2 in ...
3
votes
1answer
146 views

Extending D for four-derivatives

I'm currently trying to consistently define rules for extending D[] to four-derivatives. As 'backend' I'm using the package TRACER (http://library.wolfram.com/infocenter/MathSource/2987/), which can ...
3
votes
1answer
136 views

Downvalues vs. Scoping for Functions

Regarding my recent question on using a default value for a function argument when a pattern was not met yielded some interesting answers, but the general consensus was "Yes this can be done, but ...
3
votes
1answer
57 views

Need help in building a pattern [duplicate]

Suppose I have the following list: list = {w, r, {f, first, t, y}, {a, y}, last, {k, r, first, e}, m, e, last, r, t} I am expecting this ...
3
votes
1answer
122 views

Why even try the semantic constraints, if expression can't match the pattern structure?

This result is unexpected: Trace[MatchQ[{7}, {_?NumberQ, __}], NumberQ] (* -> {{NumberQ[7], True}} *) Why evaluate ...
3
votes
0answers
139 views

I am missing a function like HoldPattern

Temporary message: I am planning to edit this question, making the examples less confusing and by moving the things that are confusing to a separate question For any confusion about expressions that ...
2
votes
4answers
494 views

More elegant way

I read ReplaceOrRemoveInvalidOrMissingData Mathematica documentation, and I tried to apply the same approach to my dataset. I've got two problems, but one is only a style problem! There is one more ...
2
votes
2answers
317 views

Write a function that returns the logarithmic derivative

How can we write a function that if we input an expression f, it returns the log derivative $\frac{1}{f} \frac{df}{dx}$. We have to use a conditional or pattern test so that the function accepts any ...
2
votes
3answers
302 views

Select sublists with second element nearest to zero

I've got some big lists from which i need some data (one of the big lists). To be specific, I need to divide this biglists in sublists of the same length (10000), and form a new list with the mean of ...
2
votes
3answers
121 views

Applying several patterns to `Split`

Please consider the following: Split[data, patterns &] patterns=Not[#=="a"]&&Not[#=="b"]&&...&&Not[#=="blabla"]; How can I define ...
2
votes
2answers
292 views

Pattern test for variables during function definition

I am having a problem with pattern testing on variables during function definition ...
2
votes
2answers
106 views

Using FreeQ with implicit functions

In Mathematica 7, I want to determine whether a list of free of numbers greater than 1 or not. It seems like using FreeQ would be a concise way to do this: ...
2
votes
2answers
79 views

Find names similar to a given name in a large data set

I'm trying to find a 'similar' name to every item in a list ...
2
votes
3answers
153 views

How to manipulate log arguments?

A common problem I have with Mathematica is needing to manipulate the arguments of logarithms. Typically, I need to take ratios of the log arguments Mathematica gives me by default. That's to say ...
2
votes
3answers
77 views

Finding the maximum order derivative of an expression

I have an expression that is the the sum and product of undefined derivatives and their derivatives. e.g. fg+ Dt[f,t]g +Dt[g,{t,2}]f+ What I would like to find ...
2
votes
2answers
172 views

Removing trailing zeros from a list

If I have a list like list1={2334.,342.,0.,0.,2322.,0.,0.,0.,0.,,,,,,}; it's easy to remove to trailing blanks with ...
2
votes
1answer
80 views

How to efficiently process pasted content from PDF

I had selected a matrix in a PDF file, and paste it onto my MMA notebook. Below is the exact copy-pasted content: ...
2
votes
1answer
48 views

StringExpression: pattern reapeted one or more times matches pattern repeated zero times

I try to construct patterns using Riffle and Except StringExpression@Riffle[{"a", "b", "c"}, Except[{"=", ","}] ..] and expect it to match "a_b_c", but not ...
2
votes
1answer
156 views

How to create a SparseArray satisfying multiple conditions on Parts and Elements of a Matrix?

I have a matrix m1 of size $3 \times 19$. Rows $1$, $2$ and $3$ represent $3$ different groups, and columns represent $4$ different blocks: block1 - columns $1$, ...
2
votes
1answer
153 views

Add Pattern to List Removing Duplicates

Lets say I have a list of patterns ...
2
votes
1answer
60 views

Findings powers within strings - Cases function

Any idea which Cases statement will work for both A^2 and CA^4X^36 to find the powers? If I set sym to these two expressions, one requires a curly brackets around the first argument and the other ...
2
votes
2answers
101 views

how to take some parts of String with certain pattern

I have the large number of files in which the file's names follow certain pattern. for example here are names of two files ...
2
votes
1answer
88 views

What is the proper way to the pattern form Repeated in my code?

I'm matching a pattern with Repeated (..) How can I use the repeat count in the replacement rule? Example: ...
2
votes
1answer
76 views

Applying rules to rewrite expressions that contain patterns

I'm trying to write a rule that can rewrite a pattern that exists in another expression. For some reason, this is proving to be more challenging than I expected ... most likely because I'm not totally ...
2
votes
1answer
149 views

Elegant transformation of various rules to strings, {f[z_] -> y} becomes “f = @(z) y”

Assume that I have some function for transformation mathematica expressions to strings. For simplicity, just assume it is an identity: ...
2
votes
1answer
110 views

Flat function with repeated sequence

There are functions like Join[ ] that accept a variable number of arguments. Join is a flat function, as the order of arguments ...
2
votes
1answer
46 views

transformation patterns don't work with constants

I want to do the reverse of PowerExpand and convert 2*Log[x+y] to Log[(x+y)^2]. The rule: t_ Log[x_] -> Log[x^t] works for ...
2
votes
1answer
172 views

Convert boolean test function to pattern?

What is a "reverse" to MatchQ? MatchQ converts pattern into boolean function. So how to convert back? Suppose I want to use ...
2
votes
1answer
56 views

Ordering for Pattern matching in Subscripts

I have some transformation rules acting on subscripted variables. When I match the a product the order matters. ...
2
votes
1answer
50 views

Matching a list of sequences with common form

I am trying to find a pattern that matches a list of sequences that share a common form. The sequence form is: 1 followed by zero or more nonzero integers, followed by 0. An example list is: ...
2
votes
3answers
226 views

Isolating a prefactor in an analytical expression

I have a large mathematica expression that looks roughly like f = A1 Exp[a1 x] + A2 Exp[a2 x] + b1/x + b2/x^2 + c0 + c1 x + c2 x^2 where all the ...
2
votes
1answer
131 views

replacement rule to pull independent expression outside of Integrate

I'm trying to write a fairly general replacement rule that will pull expressions independent of the variable of integration outside of Integrate, since Simplify and ...
2
votes
2answers
122 views
2
votes
1answer
117 views

Simplify equations with pattern assumptions

When simplifying an expression using Simplify[expr, assumptions], the assumptions has to be explicit. Is it possible to simplify an expression with pattern ...
2
votes
1answer
109 views

Function to differentiate between date pattern and specific string format

I'd like to write a function that behaves one way when the argument is a Mathematica date, such as {2013,12,15}, or with added hours, minutes and seconds if ...
2
votes
1answer
125 views

Match a sequence of integers

I would to match a pattern p1 = 0,0,1,0,0 to the elements in listA. The elements are a boolean sequence that may look like this ...
2
votes
1answer
150 views

Using transformation rules to manipulate expressions

I'm trying out Mathematica as a replacement for LaTeX for typesetting math. It works very well, but I would like to take advantage of Mathematica's computer algebra capabilities as well. Specifically, ...
2
votes
1answer
86 views

Extracting rational coefficients from an irrational sum [closed]

I have a function that returns results that always can be represented as $p+q\,\pi^2+r\ln2+s\ln^22+t\sqrt2$ where $p,q,r,s,t\in\mathbb Q$. But the actual Mathematica expression returned not always in ...
2
votes
0answers
180 views

NDSolve Issue with initial conditions

I am trying to implement a Poincare section for a gravitational movement on the plane $(x,y)$. Here is the code I wrote ...