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4 votes
5 answers
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Transform a list of rules into a list of function definitions

I have a list of rules obtained by solving a system of equations, e.g. {f[x] -> a + 3 h[x], g[x] -> 2 a + c + 6 h[x]}. I wish to convert this list of rules ...
Stanislas Antczak's user avatar
0 votes
0 answers
34 views

How to apply dependent rules in a complex expression?

I am working with a complex expression, $L_0$, which I need to simplify iteratively using a series of dependent replacement rules. Here's the structured approach I am trying to implement: Start with ...
Charmbracelet's user avatar
1 vote
0 answers
53 views

How to Prevent Short Name Character from Auto Converting [duplicate]

The following code creates the short name character aliasdelimiter, then selects it and reads and tests it. ...
B flat's user avatar
  • 5,902
0 votes
1 answer
70 views

Transforming an expression into function

I want to transform the expression a = 2 x + 1 into f=Exp[a], z=Log[x], and express the ...
Themis's user avatar
  • 778
0 votes
0 answers
37 views

Can I remove a rule from a built-in function?

Can I remove the rule DiracDelta[n x]==DiracDelta[x]/n when n is numeric from the definition of ...
Anixx's user avatar
  • 3,692
0 votes
1 answer
28 views

How to put prime before value during a substitution?

Here is a sample Mathematica code: ...
codebpr's user avatar
  • 2,553
1 vote
0 answers
85 views

Perturbation theory. Get xAct tensor component. Substitution for xAct tensors

I work with perturbations in FLRW metric with arbitary curvature. I'm following Weinberg's book. In modified gravitation theory there is additional tensor S and I need to find it's perturbation in the ...
Ruslan Kamalitdinov's user avatar
1 vote
1 answer
57 views

How to achieve automatic nesting of pattern application

I want to apply the following rules: ...
მამუკა ჯიბლაძე's user avatar
4 votes
0 answers
138 views

Limit of a PolyLog does not work [bug]

This is an issue I am having with Mathematica version 13.1.0.0. I tried the following code, but it does not work as expected: ...
Zachary Wüthrich's user avatar
0 votes
1 answer
35 views

Cross derivative rules

I am trying to generalize the condition Derivative[1, 0][ℒp][t, ϕ] -> Derivative[0, 1][ℒp][t, ϕ]/l for $\ell$ a constant, through the following rule ...
hyriusen's user avatar
  • 155
3 votes
2 answers
176 views

Modify Rules with new patterns

My Rules always have one instance of TR on the LHS, and several on the RHS, like this TR[2] -> TR[5] + TR[h, g] I want to generalize them by adding optional ...
Albercoc's user avatar
  • 1,102
0 votes
1 answer
58 views

Weird behavior when using Parallelize with LieART

I want to perform computation with the LieART package and Parallelize some long computation. But I run into the following ...
Lelouch's user avatar
  • 545
1 vote
0 answers
37 views

Replacing an expression with pre-defined function

I am asking Mathematica to do a long calculation with functions I am defining at the beginning of the script. Because the resulting expressions are long, I want to replace them with the functions I ...
emir sezik's user avatar
3 votes
1 answer
98 views

Sort the arguments of a function using replace

I want to sort the arguments of a function f while multiplying with the signature of the permutation, i.e. f is totally antisymmetric function. My idea was something like ...
jkb1603's user avatar
  • 187
2 votes
2 answers
101 views

Why does Replace function not work the first time I try it?

Please explain why in the following mathematica code, the cos term was not replaced in the first try, but got replaced in the second try? ...
Prem's user avatar
  • 121
2 votes
4 answers
297 views

Ignore higher order terms in an expression

I am trying to ignore terms that are higher order (third or more) in an expression. For example, for the input function: $$f_{in}= \alpha\beta + \alpha^2 + \beta^2 + \alpha\beta^2/2 + \alpha^2 \beta $...
Arnab's user avatar
  • 123
0 votes
0 answers
52 views

Mathematica solve with conditions on constants differ from replace

I have been trying to solve some complicated linear equations in Mathematica, with variables $y_{i}$, and constants $a, f_{j}$ where $0\leq j\leq10$. I only care about the case where $\sum_{i=1}^{10}...
wsz_fantasy's user avatar
4 votes
1 answer
127 views

How to write a rule that matches alternatives but return one of them always?

Consider the following rule: $rule={"Period ID"|p:"Period":>p}; This rule will match ...
user13892's user avatar
  • 9,651
3 votes
1 answer
107 views

How to `Collect` where `var` is one expression?

Edit: Clear["Global`*"]; expr1 = (a + c - b + 1)^3 + (-b + a + c + 2)^4 // Expand For test case expr1, this is the ...
138 Aspen's user avatar
  • 1,902
0 votes
0 answers
38 views

Replacement not working as desired [duplicate]

The following replacement works fine ReplaceAll[1/F[x],F[x]->y] (*1/y*) but this doesn't ...
qreus's user avatar
  • 343
6 votes
4 answers
346 views

Transform sequence into ragged list

I want to transform seq = {x, 1, 2, x, 3, x, 4, 5, y, y, 67, y}; into {1, 2, {3, {4, 5}}, 67} The only way I found is rather ...
eldo's user avatar
  • 82.5k
0 votes
1 answer
64 views

Why does Mathematica fail to substitute some terms in an expression but not others?

I have an expression of the form: $A-\frac{e^{-t/t_1} \; a \; b}{c \; t_1} \; U_1 - \frac{e^{-t/t_2} \; a \; d}{c \; t_2} \; U_2 -\frac{e^{-t/t_2} \; a \; e}{c \; t_2} \; U_2 - \frac{e^{-t/t_3} \; a \;...
CountBackwardsFromInfinity's user avatar
4 votes
4 answers
300 views

Replacing string values with one of the sequence-functions

Given the following list of rules (which might contain duplicate keys), I want to replace the string values with the first preceding numerical value. ...
eldo's user avatar
  • 82.5k
1 vote
0 answers
43 views

Why list of replacement does not work in the following example? [closed]

I want to replace a long list but in the following format, but it does not work: (Aa + Bb + Cc) /. {{Aa, Bb, Cc} -> {x + 2, y + 2, z + 2}}
SciJewel's user avatar
  • 575
1 vote
0 answers
59 views

Replacement rule runs for a long time [duplicate]

I have a simple expression that reads (some expression in b) q^(8/3): ...
Lelouch's user avatar
  • 545
1 vote
1 answer
41 views

How to do this replacement? Match the variable, but not the function [duplicate]

I have the following expression: $$\frac{\left(-2 \lambda \lambda [\theta ]+\lambda [\theta ]^2+\lambda ^2+\lambda \right) \lambda '[\theta ]^2}{\lambda [\theta ]^2}$$ I want to replace every ...
AccidentalTaylorExpansion's user avatar
1 vote
0 answers
40 views

Difference in pattern matching between Cases and ReplaceAll (Already searching at all levels and heads)

Why is there a difference between the pattern matching between Cases and ReplaceAll in the following: ...
Kvothe's user avatar
  • 4,651
1 vote
0 answers
60 views

Random replacement in array

In the spirit of this interesting article of Stephen Wolfram I also decided to study some issues related to mutations. I’m working with simple {0,1} arrays and I’ve ...
lesobrod's user avatar
  • 1,904
1 vote
1 answer
82 views

How to replace C[1] in solutions of trigonometric equations into k?

This is my code Table[{HoldForm[Cos[3 x + 2 Pi/5]] == Sqrt[i]/2, Reduce[Sin[2 x] == Sqrt[i]/2, x, Reals]}, {i, 0, 4}] How can I replace C1 to ...
John Paul Peter's user avatar
3 votes
2 answers
103 views

Multiple replacements in a long expression

Why does the replace /. not work on the second argument in the following expression: ...
SciJewel's user avatar
  • 575
0 votes
0 answers
31 views

Time Complexity of Multiway System

I was wondering what the time complexity for the implementation of a Multiway System would be. For reference, we can implement a MultiwaySystem using the Resource Function ...
Navvye's user avatar
  • 171
2 votes
1 answer
81 views

Generate variables in multiple integral

I want to do a multiple integrate with n variables. When I change the value of n, I do not want to rewrite the variables in the integral manually like here: ...
Zsombor's user avatar
  • 185
2 votes
1 answer
77 views

Removing `circular rules'

Say that I have a huge list (>300.000 elements) of polynomial equations and I want to simplify these by looking for some simple equations of the form x[i] == _ ...
Gert's user avatar
  • 1,620
5 votes
3 answers
380 views

Reversing the order of function arguments by a replacement rule

I am facing an issue when I try to reverse the arguments of a function in a replacement rule. Let me give an example : ...
Adrien Martina's user avatar
1 vote
0 answers
39 views

Performing difference in extracting coefficients from a sum

I have an expression ...
Lelouch's user avatar
  • 545
2 votes
2 answers
61 views

Difference between variables and expressions for ReplaceAll

I'm doing some GR calculations with xAct. I get an expression that is heavy. In order to simplify the results, I try to use the function ReplaceAll in simple cases. ...
TrodaroX's user avatar
4 votes
5 answers
217 views

How to make expression-dependent replacements?

Consider as a toy example that I want a replacement which acts on {x,1,2,3} by replacing $x$ with the length of the list itself. In this example this should output ...
Adrien Martina's user avatar
9 votes
5 answers
382 views

Reconstruct list from its PositionIndex

Is there a more elegant or shorter way of reconstructing a list from its PositionIndex? The following I regard quite cumbersome: ...
azerbajdzan's user avatar
  • 21.3k
11 votes
5 answers
522 views

Isomorphic lists

Is there a function that outputs True if lists are isomorphic (there exists a rule that changes the first list into the second one and inverse of the rule changes ...
azerbajdzan's user avatar
  • 21.3k
2 votes
0 answers
123 views

How to effectively substitute variables in xAct?

I am trying to find the gauge field equation by varying the Born-Infeld Action with the help of xact package. I use the following ...
codebpr's user avatar
  • 2,553
1 vote
1 answer
57 views

Set the value of a parameter in a Series expression [closed]

I have a lengthy expression resulting from a series expansion in some dummy variable $e$ which I now wish to set equal to 1. However, when I try to use a ReplaceAll ...
Matthew Ward's user avatar
7 votes
3 answers
270 views

Replace number in string with ? and /;

I am trying to make the following: StringReplace[{"A4", "A#3"}, {"A" ~~ x_ -> "B" ~~ x}] This should replace ...
Red Banana's user avatar
  • 5,441
3 votes
1 answer
43 views

How to Replace EdgeLabel in a Graph [duplicate]

I am working with Graphs in which I want to define a Graph with Symbols or Strings as EdgeLabels, and later replace these with functions of the symbols with symbols then replaced with numerical values....
David Keith's user avatar
  • 4,604
1 vote
1 answer
64 views

Rules Being Ignored by Mathematica

Can someone explain to me why Mathematica is ignoring the replacement rules in the following code: ...
Mjoseph's user avatar
  • 255
6 votes
1 answer
109 views

Substitute solution into ODE to verify it holds

I am struggling a lot to understand how to do the very basic exercise of substituting a solution into an ODE so see whether the solution is indeed valid. Consider the following ODE: ...
NC520's user avatar
  • 479
1 vote
2 answers
99 views

How do you remove parts of an element within a list? [closed]

I have a data set that is something like: time={-2_ms, -1_ms, 0_ms, 1_ms, 2_ms}; How do I drop the _ms part such that its just a list of numbers?
Alex Wong's user avatar
9 votes
2 answers
509 views

What's the difference between With and ReplaceAll?

A wolfram Tutorial mentions that ReplaceAll and With are similar: The way ...
ions me's user avatar
  • 1,055
2 votes
1 answer
148 views

How to correctly replace scalars with matrices?

How can a scalar be replaced with a matrix to perform operations on the matrix, not its elements? For example, ...
homocomputeris's user avatar
2 votes
1 answer
79 views

Why can't I assign upvalues to NonCommutativeMultiply?

I'm trying to define a non-commutative product with respect to which, certain quantities (e.g. numbers, and some other quantities defined in my code) behave as "scalars" and can be pulled ...
user366202's user avatar
1 vote
1 answer
41 views

How to check a group of solutions of partial differential equations?

There is the partial differential equations, $$ \left.\left\{\begin{array}{c}u_t-3qu^2u_x+\frac{3}{2}q(uv)_x-\frac{1}{4}qu_{xxx}=0,\\v_t+\frac{3}{2}qvv_x-3q(u^2v)_x+3qu_xu_{xx}+\frac{3}{2}quu_{xxx}-\...
godspeed's user avatar

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