# Tagged Questions

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

99 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 ...
133 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 ...
152 views

### How can I extract all the non-number symbols from an expression [duplicate]

If I have an expression, let us say something like this: Cos[3 x] + π/cofe Exp[y^(c z)] how can I get all non-number symbols in the expression which are: <...
240 views

### CSS Selectors for Symbolic XML

Symbolic XML is a convenient way of managing XML in Mathematica, at least for casual use or small tasks. Here and elsewhere you can find examples of XML handling in Mathematica, including XSLT/XPath ...
179 views

### Searching for phrases in a block of text

One could call this a pattern finding question with dictionary (or WolframAlpha) lookup, but let me give you some background first. I have a couple of friends who are trying to improve their English ...
50 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 ...
214 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 ...
97 views

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

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 ...
163 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 ...
67 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 ...
77 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 "a_bc"...
76 views

### How can I get the functionality of a command ReplaceAllList?

I'm trying to use ReplaceList to match subexpressions. I expected the command: ReplaceList[{p, {p, p}}, {x_, y_} -> x y] to output two results, equivalent to: ...
194 views

### StringCases using RegularExpression fails when there is missing data

I got some text scraps with this structure "Focal Plane: 198' Active Aid to Navigation: Yes *Latitude: 35.250 N *Longitude: -75.529 W" But some of them lack ...
115 views

### Pattern matching and HoldForm

Create rules based on data. I have a system that picks out on date,based on some rules. I then want to generate a new rule based on this date and apply the rule to a new dataset. ...
101 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: ...
1k views

### Detecting patterns of black and white stones on a 2D board

I'm writing a program to play a game of Pente, and I'm struggling with the following question: What's the best way to detect patterns on a two-dimensional board? For example, in Pente a pair of ...
93 views

### Pattern matching with PDF, Distributed and multivariate distributions

I have defined a function to compute the Shannon entropy of a probability distribution: ent[p_] := Expectation[-Log[PDF[p, x]], x \[Distributed] p] This works ...
340 views

### Formatting text through pattern matching

I am trying to format some text based on some patterns. ...
114 views

### Name scope confusion

Sorry for the too ambiguous title. First consider a following code snippet. ...
141 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. ...
52 views

### Can Mathematica find the discriminant formula? [duplicate]

This question is not really practical, but rather a curiosity question. Can Mathematica solve a quadratic equation without its discriminant? I mean, whenever it see a quadratic equation it tries to ...
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 ...
223 views

### Finding similar expressions in list

I have a function that returns to me lists of expressions, like: ...
74 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: ...
88 views

### Function behavior based on Head

I'm figuring how to implement a function behavior based on the Head of its argument. I mean ...
765 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 ...
616 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 ...
205 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 ...
281 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 ...
143 views

### Selecting expressions from a sequence that are not subexpressions of earlier elements

I have a While loop that generates and prints an expression on each iteration (there can be thousands of iterations). UPDATE: Some expressions are generated in ...
268 views

### Replace matrix with conditions

I want to replace the values of 1. in slot under the condition that the year and month in basevalue and ...
319 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 ...
552 views

### How to do Cases with multiple related patterns?

I would like to write a function similar to Cases, but can search for a group of related patterns together. For example, ...
741 views

### Counting sublists containing 0

Given a list: data = {{0, 2}, {0, 0}, {1, 0}, {1, 2}, {2, 3}}. I would like to count the number of sublists which contain zero. ...
25 views

### Manipulating named patterns inside replacement rules [duplicate]

When I evaluate the following expression, {a -> "value1", b -> "value22"} /. {Rule[x_, y_] -> Rule[x, y]} I get ...
264 views

### How to define function that can change patterns

Given time series data as follows: data = {{{2011, 1, 13}, 10}, {{2011, 2, 14}, 17}, {{2011, 3, 15}, 20}, {{2012, 1, 16}, 30}, {{2012, 2, 17}, 40}}; ...
169 views

### Checking through an expression

I am writing a code that manipulates expressions that contains functions with an arbitrary number of arguments. An example expression is ...
109 views

### Elegant way to match a list with only certain types of elements

I'm working on learning Mathematica programming for personal edification and am trying to find a more elegant way to do a matching expression which will match only a list containing elements that are ...
266 views

### Extracting argument sequences from function expressions

Why is it that fun[x, y] /. fun[z__] :> z leads to Sequence[x,y] but ...
233 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 ...
224 views

### Pattern matching

This is a very simple question I hope you can help me with. I am experimenting with pattern matching. I want to write a pattern for a difference between two symbols, ...
100 views

### Dot when used in a pattern becomes Times… Why?

In[1] := Hold[a.b] // FullForm Out[1] := Hold[Dot[a,b]] So far so good. ...
356 views

### Using Except with strings

Suppose that I have the following sample list, called list: list = {"bBb", "aAa", "aaa"}; Now suppose I want to select the ...
101 views

### Pattern-rewriting Pattern triggers error?

I am trying to rewrite patterns. For example, I'd like to rewrite the pattern jFoo_Integer which has FullForm ...
285 views

### Orderless pattern matching of rule lists

I am looking for a compact way to specify a pattern to match a rule list with MatchQ that allows for enumerating the rules in the rule list in an arbitrary order. E....
261 views

### Bug in RepeatedNull?

RepeatedNull appears to be buggy (versions 8.0, and 9.0). Define f as follows: ...
238 views

### String pattern matching & replacement

I would like to find all occurrences of a full stop "." followed by a capital letter in a string and have these replaced with a "; ". How do I do this in Mathematica? e.g. ...
341 views

### Is there a more Mathematica-y way to label these plots?

I am studying an infinite square well in the context of quantum mechanics. ...