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

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0
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1answer
80 views

How to ensure efficient order of operations for rules, slots, substitutions?

I need to calculate several functionals Q[[t]] of a pdf f[x]. ...
0
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1answer
48 views

Replace all instances of Integrate by NIntegrate and add a Method option

I have an analytic expression which involves several integrals Integrate[f[x], {x, lb, ub}] where the functions f and bounds ...
0
votes
1answer
82 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 ...
0
votes
1answer
45 views

Specifying string patterns in a plain text

I need to extract three data, like that: (1.05, 1.37,A) from an imported list of plain texts: "... Syntax of parallax is : 'value quality [error] bibcode' value : parallax value quality : flag ...
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votes
0answers
13 views

Comparing association using MatchQ [duplicate]

For me below query results into False.I expect it to return True. ...
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0answers
38 views

Where can I find mathematica documentation about @@@? [duplicate]

For example, to build a rule from 2 lists {a,b,c},{1,2,3},I use : Rule @@@ Transpose[{{a, b, c}, {1, 2, 3}}] : {a -> 1, b -> 2, c -> 3} OK, but how @@@ works ? (Black magic for me) I am using ...
0
votes
1answer
88 views

Can we say that “all functions in Mathematica are some kind of pattern-matching-and-replacement procedures”? [duplicate]

Currently I am studying Mathematica programming, and when I study pattern matching and replacement, I find it is quite similar to functions. So can we say "all functions in Mathematica are some kind ...
0
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0answers
50 views

“Meta-matching” patterns [duplicate]

The title refers to the general problem of writing patterns to match pattern-containing expressions (hence "meta-match"). Here's an example. In the following rules ...
0
votes
0answers
56 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: ...
0
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0answers
71 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 ...
0
votes
0answers
42 views

How to correctly use PatternTest (?) [duplicate]

This works fine: {3, -5, 2, 7, -6, 3} /. x_ /; x < 0 :> 0 (*{3, 0, 2, 7, 0, 3}*) and this works fine: ...
0
votes
0answers
29 views

Problem with replacing a head with another head using pattern [duplicate]

Why would this work Times[a, b, c, d] /. Times :> List (* {a, b, c, d} *) but this doesn't work (the Times still remains ...
0
votes
0answers
48 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 ...
0
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0answers
23 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 ...
-1
votes
3answers
105 views

How do i import a list of files, choosing the name

I have this list of files, i'm using FileNames[{"*.txt"}, NotebookDirectory[]] to import it, but i just want the ones without inelastic on the name. How can i select just by the name? Thanks ...
-1
votes
2answers
184 views

RotateRight ith row of a matrix by i - 1

first time stack exchange poster here! So I was working on a problem, the purpose of which was to write a function in the procedural style to rotate right the ith row of a matrix by i - 1 spaces. Ok, ...
-1
votes
2answers
69 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 ...
-1
votes
2answers
540 views

Correct way to compare arrays and do conditional evaluations

I would like to compare two arrays a=: and b= and get: using: (b/.(b_?Positive->a+b))//MatrixForm but this doesn't seem to work? Can ...
-1
votes
3answers
199 views

How to systematically classify Mathematica expressions?

How to systematically classify Mathematica expressions? I can think of using Head[], Depth[], ...
-2
votes
1answer
243 views

How to set a rule in pattern matching to change a string from one form to another

I want to define a rule that will change a particular type of string to another form. For example:- a string having ...
-2
votes
0answers
25 views

“Extract” certain elements of a list of “rules”? [duplicate]

I have the following list: {u1[0] -> 3773.62, u2[0] -> 3773.62, u3[0] -> 48.7871} I need to extract the elements on the right hand side of each rule ...
-3
votes
2answers
93 views

Write a function, write a pattern [closed]

I have the following list: list = {{1, 2, 4}, 6, 7, 8, {8, 2}, {3, 4}, {4, 5}, {1, 2, 3, 1}}; (a) I should write a predicate-function in combination with an ...