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

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6
votes
3answers
182 views
2
votes
1answer
76 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 ...
14
votes
5answers
713 views

Getting number of binary digits combinations without “forbidden” patterns

I need to get the number of all combinations of binary digits in an 8-digit binary number, but not including those that follow some "forbidden" patterns like these: ...
2
votes
1answer
36 views

Linear function on strings using UpValues

I have two functions Sup and Sdown that take a string of letters with allowed characters ...
4
votes
5answers
493 views

How can I name patterns in a Switch expression?

Suppose I have an expression and want to match it against successive patterns and return an expression corresponding to the first pattern that matched. In that case, I can use ...
14
votes
1answer
283 views

Why is ReplaceAll behaving like this?

I'm learning to use the ReplaceAll function and I found the behavior of which is quite confusing. For Sqrt[f[x, y]] /. f[___] -> u Mathematica returns ...
10
votes
4answers
435 views

Building a tree

Given a list of word characters, such as this one, I'd like to build a tree, similar to this makeTree function, but with the tree in a different format. So, for an input such as ...
1
vote
0answers
72 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 ...
4
votes
6answers
367 views

Command to take the first elements of a list that match a pattern

I want to find the number of elements in a list in a row that match a certain pattern. So for this list {1,1,1,1,0,0,0,1,1,1} It should return "4" because there ...
0
votes
2answers
73 views

How do I tell pattern searcher the order in which to search for patterns given in general form?

I have a really long sequence of Symbols inside a function, say nonCommute[a,b,c,e,e,f,g,b,i,j], and I am implementing a ...
3
votes
2answers
91 views

Removing non-word characters in certain parts of a string

I would like to ask how I can remove non-word characters from a string, but only in certain cases. I have read this article, so I know how to get the words out of a string. My text is however a bit ...
3
votes
1answer
75 views

FreeQ and arguments of Hypergeometric2F1

I was trying to use FreeQ to test for the presence of Hypergeometric2F1 functions in my expressions. I encountered the following ...
1
vote
0answers
56 views

Understanding the order of applying Rule to expression [closed]

I am a little confused about: In what order is a Rule tried to apply to an expression? In a depth-first order or otherwise? For example, ...
2
votes
2answers
125 views

Matching a case when one element in a pair is Null

I've got a dataset of laitutdes and longitudes. Unfortunately, some of the dataset was from when a time when lat/longs weren't constantly recorded. So I need to remove the invalid data before working ...
6
votes
2answers
209 views

Apply Trig Identity to Transform Sum of Sinusoids into Phase-Shifted Cosine Function

I'm trying to solve for the output of a simple RC low-pass filter, with Cos[w t] input. The convolution of the input with the RC transfer function gives me the right output, but I'd like to be able to ...
2
votes
3answers
120 views

Cases do not return all expected result

I have the following line code: Cases[g[h, r, t, b, m], x_[__, y_, __] -> y, {0, -1}] I am expecting the results to be ...
3
votes
1answer
134 views

Recognizing Matching Colors in a Game Grid from a Camera Image

I am relatively new to Mathematica, having taken my first serious dive into it this week. As a fun project to teach myself some of the basics, I've come up with a goal of optimally solving a game ...
3
votes
3answers
77 views

Pattern for finding matches that are different [duplicate]

I am trying to solve the following problem. I have tuples of size 3 {{a, b, c}, {a, b, c}, {a, b, c}} I would like to find cases where all the elements in a ...
5
votes
4answers
157 views

Finding the position of a single array in a list of arrays that contains wildcard variables

Consider two lists: superList = {{wc,wc,1,wc,wc}, {wc, wc,2, wc, wc}, {wc, wc, 3, wc, wc}, {wc, wc, 4, wc, wc}}; littleList = {a,b,3,c,25}; In ...
4
votes
4answers
170 views

Sublist pattern matching

Is there any way to simplify the following pattern: {p___, {a___, x_, x_, b___}, q___} :> {p, {a, x, b}, q} Ie. where I remove duplicated elements within ...
4
votes
3answers
131 views

Pattern match for nested Association

Suppose I have Association testAssoc=Association[a->Association[1->1,2->2],b->Association[1->1,2->2]] which ...
1
vote
2answers
91 views

text analysis: split document in seperated lines

For a text analysis I want to split a large document in seperated lines. Then I want to calculated for example the average number of words. A example of the document is the following: ...
5
votes
4answers
253 views

Pattern matching - comparing two lists

I would like to compare two different lists to see if the shorter one is a member of the larger e.g. is the list {2,3}, with that sequence of elements, a member of {1,2,3,4,5}? I have tried using ...
5
votes
1answer
185 views

Sentiment analysis of tweets

I want to use Mathematica for a sentiment analysis on tweet-messages. For that purpose i selected several tweets. Each tweet is interpreted by myself as positive (pos) of negative (neg). For example: ...
3
votes
2answers
143 views

Convert matrix rows into variables

Can anyone show me how to set all matrix rows to variables. For example, I have matrix w={{1,2,3},{3,2,1},{0,0,0}} and I need to set each matrix row to be separate ...
8
votes
1answer
281 views

Mma10 mystery: Failure of pure function substitution with Interpretation?

Bug introduced in 10.0.0 and fixed in 10.0.1 I had code to display with subscripts from Displaying index as subscript on output: e.g. C[i] -> C_i with Notation[...] or Interpretation[..]? which ...
13
votes
1answer
98 views

Report: IgnoringInactive: a bug?

Bug introduced in 10.0.0 and fixed in 10.0.1 Just to report. IgnoringInactiveshould work with Cases. In agreement with the ...
1
vote
1answer
93 views

Function returned an unexpected list

I was trying out a question in Wellin's Programming with Mathematica that says the following. Question: Given a set of points in the plane (or 3-space), find the maximum distance between any pair of ...
12
votes
4answers
621 views

Calling Table with custom iterator

I often find myself in situations where I, for example, need to build a table for some expression, but want to set the number of points rather then the step size, so the code ends up looking like this ...
1
vote
0answers
45 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: ...
11
votes
4answers
265 views

Recognizing special cases of a defined function for permuted arguments

I have a number of ugly ways to implement the following pattern recognition task, but I'm looking for something elegant to keep my notebook tidy. I need to define a function of six variables ...
7
votes
5answers
389 views

Splitting strings at lower case characters and numbers

I'm trying to split the strings of chemicals into their elements and numbers. See this example "Fe3O4" will be split into ...
6
votes
5answers
414 views

The correct pattern for Cases

I have a problem that, admittedly, I have already solved using Select instead, but it is irking me that I cannot seem to construct the right pattern to solve it ...
0
votes
0answers
52 views

On the order of rules specification [duplicate]

I wanted to understand how Mathematica parses function definitions in rules-based programming, so I started with the simple code: ...
6
votes
5answers
368 views
10
votes
4answers
389 views

What is the correct way to use specific rule for specific pattern match when parsing an expression?

update: Thanks for the answers below. But I noticed they do not handle the following special cases: lis=1 and lis=z , ...
0
votes
0answers
68 views

Making a list of terms ordered by product order

I have some expressions f,g,h that are elements of a symmetric tensor algebra. The expressions are generated by a basis ...
1
vote
3answers
76 views

Store matched variables

Edit: I am matching and replacing a particular expression. At the same time... I want to store matched variables for later use. I got it to work with messed up code involving ...
14
votes
1answer
392 views

Quick way to use conditioned patterns when defining multi-argument function?

I have a simple function that is supposed to only accept numeric values (i.e. complex/real numbers and constant symbols e.g. Pi, E). $$f(a,b,c)=a+b+c$$ Edit: I should have chosen a less simple ...
0
votes
3answers
84 views

Unexpected behavior of rule-replacing with string concatenation [closed]

Here's the code. Clear[x,y,z]; {x,y,z} /. x_ :> ("^_^" <> ToString[x]) I get the result ^_^{x, y, z}, which is not ...
2
votes
1answer
120 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 ...
4
votes
1answer
125 views

What would be a pattern for a general row of an identity matrix?

I know this is a novice question but I would like a pattern for a list containing zero or more zeros followed by exactly one 1, followed by zero or more zeros. Something like: {0___,1,0___} But ...
2
votes
3answers
104 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 ...
17
votes
2answers
386 views

Pattern that matches colors

Suppose I'm writing a function that takes a color as a parameter; for example: drawShape[color_] := Graphics[{Style[Disk[], color]}]; But if the caller inputs an ...
6
votes
3answers
208 views

Problem with WordBoundary in string patterns

I am trying to extract from a string all words that end with "-man", but the problem is that WordBoundary does not seem to work as it returns whole string ignoring ...
1
vote
2answers
65 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 ...
1
vote
4answers
174 views

Need an efficient way to do this list manipulation

Lets say i have two lists with me as given below: l1 = {4, 6, 8, 9, 10, 12}; l2 = {2, 3, 4, 5, 6, 7}; Now i have a function S2P(details irrelevant) which takes ...
3
votes
2answers
269 views

Using ReplaceAll to replace a head

Why would this work to replace the head b with newHead: ...