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

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3
votes
2answers
192 views

Consecutive identical integer members of a list

Can you help me to find and count sub-sequences of consecutive, identical integer members of a long list (at least 1000 members)? By sub-sequences I mean runs like ...
1
vote
1answer
81 views

Can I map a function over a sequence of arguments without making the arguments into a list first?

I would like to set evenFunction[f_][a_, b_, c_, ...] = f[Abs[a], Abs[b], Abs[c], ...] I have come up with two ways to do this so far. Use pure functions <...
6
votes
1answer
104 views

Find subsequence A in sequence B A007908 - OEIS

I have sequence A as A007908 - OEIS and pattern B which is a sub-sequence of that sequence A. I need to find index of first occurrence of the given pattern. For example pattern ..1010... I've looked ...
9
votes
3answers
213 views

How to make a ReplaceAll Rule for adjacent items in a list?

I would like to make only one pass of a list of 2D items and replace adjacent items that have matching $x$ or $y$ coordinates with a series of linearly interpolated points between the two points. My ...
3
votes
2answers
95 views

How can I filter a permutation list depending of a pattern? [closed]

I've created a permutation list Grid[Permutations[{a, e, q, r, t, u}], Frame -> All] and only want to see rows where the 5th element is a "t". I tried to do ...
4
votes
2answers
274 views

How do Reap and Sow work in this context

I have a list of points in 3D and I need to count how many times each point is repeated. For a similar problem with a list of characters many different solutions have been proposed in this post: ...
1
vote
1answer
36 views

ReplaceAll - Position of list arguments not displayed properly [closed]

This code A[1, 2, 4, 5] /. A[a___] -> Position[{a}, 4] return {} Why this code not return 3 (a position of number 4) ? I ...
-1
votes
2answers
70 views

What would be a pattern matching only numbers that are not real?

I wanted to delete all complex numbers out of a list, and I tried the following, but it didn't work. Suggestions? Im[x] != 0
2
votes
0answers
59 views

How do I let Fourier Transform know that it is a linear operator? [duplicate]

I have the following issue with FourierTransform, Fourier transform doesn't seem to know it is a linear operator. ...
1
vote
2answers
40 views

“Nonatomic expression” error when identifying certain positions in a list [duplicate]

Please can anyone help ? I have a list of sets, and I am trying to find the positions in that list of those sets which are subsets of a given set. (Here I am ignoring the distinction between lists and ...
2
votes
1answer
59 views

Braces in pattern with Cases function

Here's my problem: I've got a JSON-formatted response and want to match some variables over the response. I'm doing it using Cases: ...
6
votes
3answers
145 views
6
votes
2answers
99 views

Pattern matching an expression involving Times

I'm trying to write a Mathematica function that will format expressions according to my preferences, for example displaying (5 c x)/Sqrt[2] as ...
8
votes
1answer
164 views

Why does pattern test work only with pure functions?

Why is it that pattern test works only with pure functions? Cases[Range[0, 70], _?(Divisible[#, 7] &)] Cases[Range[0, 70], x_?(Divisible[x, 7])] I ...
5
votes
1answer
78 views

Transformation rules to distinguish common variable with Subscript and OverBar $x,x^2,\bar{x},\bar{x}^2, x_p,x_p^2, \bar{x}_p, \bar{x}^2_p $

I am looking for help in writing transformation rules in which I wish to distinguish between eight variables $x,x^2,\bar{x},\bar{x}^2, x_p,x_p^2, \bar{x}_p,\bar{x}^2_p $. For each of these eight ...
1
vote
3answers
162 views

Making a replacement on the numerator and denominator of a rational number

It's isn't a big deal, but when I run the following I don't get the output I expect. After discussing this in the comments it appears it has to do with being an atomic expression. ...
0
votes
1answer
55 views

Avoiding misconversion of data with ToExpression function [closed]

I've got a list of data with the following structure which can be easily converted To expresion by some manipulation such as ...
13
votes
6answers
338 views

How can I mix the behaviors of StringReplace and ReplaceAll in a single rule?

I'm trying to take a list of the form { {"65 + 3 months", 75}, {"65 + 4 months", 75.1} }, and transform the string part to a number such as 65.25 or 65.333, ...
14
votes
2answers
693 views

How to detect loops in a vector field?

Given a vector field and I'd like to detect if there are streamlines in closed patterns. For example, if the input is a vector field like this: ...
9
votes
2answers
239 views

Pattern and Orderless function

I'm a Mathematica beginner. I am exploring the use of patterns and (only for fun) am trying to implement a permutations function. My (dirty) code is: ...
1
vote
2answers
65 views

Substituting a list of values into a function [closed]

g[p_] := Mod[19^(-1 + p), p^2] This is my function, and the set of values I have is the first 999 prime numbers. I made a table listing the first 999 prime ...
6
votes
2answers
212 views

ReplaceAll problem

Bug introduced in 10.1 and persisting through 10.2 or later Confirmed, as bug, by WRI: [CASE:3402234] I am trying to combine terms of the type ...
23
votes
1answer
228 views

Strange behavior with Cases and Position with SetDelayed

I feel like I must be missing something simple and obvious here, but this has me scratching my head. This works as expected: ...
1
vote
2answers
77 views

Patterns with inactive integrals

I am trying to do algebra on unsolved integrals but not getting the pattern-matching right. I want the correlation of f[x] and f[x]+a*d[x], normalized by their self correlations. ...
5
votes
3answers
131 views

Matching Symbol or Subscript, but not Symbol arguments of Subscript

I'm trying to get a list of all the variables in a symbolic expression. Some are named with Symbols, some are named with ...
0
votes
4answers
236 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? ...
3
votes
3answers
100 views

How to compare and remove x-coordinates (and the associated y-coordinates) that are less than previous x-coordinates?

I am using Mathematica version 9.0 and am trying to compare and remove x-coordinates, and the associated y-coordinate, that are less than previous x-coordinates. Below is an example using sample data. ...
8
votes
1answer
310 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 ...
2
votes
1answer
147 views

Select largest number using pattern

I have the following expression: myExpr=R[C[2],B].(II+R[C[3],C[2]].(II+R[C[4],C[3]])) I need to create a pattern which would replace the ...
0
votes
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 ...
4
votes
4answers
264 views

Replace matrix rows conditionally while avoiding For loop

I have the following variables: myMatrix={{0,0,0},{0,0,0},{0,0,0},{0,0,0},{0,0,0},{0,0,0}} myIndices={1,3} I need to replace the rows ...
2
votes
1answer
72 views

Confusion over blank sequence in pattern matching

My overall goal was to produce a list of heads used in a graphics output. For an example I used: ...
3
votes
3answers
159 views

Find position avoiding For loop

I have a list: {a,b,c,d,e,f} And a function sizeFunc[element_] which returns the size ...
3
votes
3answers
256 views

Help with PatternSequence

I have a list of strings of the form list = {str1, str2, strx, str3, .., str10} each string contains both letters and numbers, except for ...
2
votes
1answer
67 views

Dropping rational coefficients

I have a list of expressions (they all are exact numeric quantities, not containing any variables), some of them have integer or rationals coefficients, or complex coefficients with rational or ...
6
votes
5answers
791 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 ...
2
votes
2answers
78 views

Trouble simplifying using Replace

I have the following expression: w.a.b.r+w.c.d.r I want to get: w.(a.b+c.d).r So far I used ReplaceRepeated: ...
8
votes
2answers
163 views

An equivalent to Condition that I can use anonymously when string pattern matching

When I name a pattern I'm working with, that name stands for the same particular expression wherever it shows up. That's a basic precept of how the Wolfram Language's pattern-matching works. But if I ...
0
votes
1answer
182 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_ ...
3
votes
3answers
299 views

How to identify all rules that match pattern type? [duplicate]

I would like to be extend the below solution to be able to find get all rules from the list step[2] that match the generic pattern k_Digit_p. Where k and p are not ...
1
vote
1answer
60 views

How to use EvenQ[] in patterns? [duplicate]

This works: (w[1] + w[2] + w[3]) /. w[s_] -> If[s == 2, w[s], 0] (* w[2] *) This doesn't: ...
7
votes
1answer
149 views

How to Negate a Pattern Test and Transform a List of Strings to a JSON array

First I would like to find out how to negate a pattern and based on this I would like to solve this little problem on how to transform a list of strings to a JSON array. This is how I started working ...
0
votes
2answers
106 views

Delete Element within a List based on the Order [closed]

I want to do the following, deleting the element of a list that do not match an increasing order as example: {1,2,3,4,6,5,7,8}->{1,2,3,4,6,7,8} I've thought of using DeleteCases but I'm not able to ...
21
votes
2answers
819 views

How to inject an evaluated expression into a held expression? [duplicate]

I know that there are methods to structurally manipulate held expressions (discussed e.g. here), but I failed to apply those for this particular problem: ...
5
votes
2answers
407 views

Opposite of Alternatives

I was looking at this question (here) and I tried to find any thing gives the opposite of Alternatives. In other words, some pattern matching function that gives ...
11
votes
1answer
307 views

Empty Blank regression in v10.1

Bug introduced in 10.1 and fixed in 10.2.0 In v10.1.0.0 on Linux, when Blank[] is used in Alternatives with pattern that can ...
4
votes
2answers
188 views

Is there any way to use head of Real and Integer altogether?

Is there any way to use the head of Integer and Real together like below? The below is not right, I know that, it is just for ...
2
votes
2answers
197 views

How to make a function that yields a number under power operator by using pattern matching?

Can I ask you a question related to function and pattern? I would like to make the function below work which doesn't yield return values I expect. How can it be done? ...
8
votes
2answers
326 views

Unexpected behavior of rule matching a pattern

I am a beginner exploring the world of Mathematica. I expected the following code T[6, 5, 4, 1, 2, 3] /. {T[a___, 1, b___] -> Length[List[b]]} should return ...