Questions about Mathematica's rule-based replacement functionality, including functions such as Rule (->), Replace, ReplaceAll (/.) and ReplaceRepeated (//.).

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0answers
25 views

Simplifying self-reciprocal rational function [duplicate]

I have trouble transforming self-reciprocal rational functions in one variable like ...
5
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3answers
91 views

How can I pass replacement rules to a package-defined function and have it understand their context?

I am writing a package where I would like to be able to pass replacement rules to a function inside the package and have the function manipulate its symbols using those replacement rules. However, I'm ...
1
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1answer
61 views

how to replace one calaculation result to another one in a loop?

I am doing the calculation in a loop. I gain a digit for rzin in ...
8
votes
0answers
148 views
1
vote
1answer
47 views

How to substitude a^n->D[u[t,x],{x,n}] for n=0,1,2,

I have expression which have terms a, a^2, a^3, ..., How can I replace a^n -> D[u[t,x],{x,n}] for n=0,1,2,....
2
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0answers
34 views
1
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3answers
122 views

Symbolic differentiation [closed]

I have two symbolic differential equations and I want to used them in another equation as follows: ...
14
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3answers
229 views

ReplaceAll with Associations instead of Rules

I have just noticed that x /. <|x -> 123|> evaluates to 123 In other words, the association seems to behave as a ...
3
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0answers
84 views
1
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1answer
37 views

ReleaseHold NIntegrate after Replace variable

I would like to calculate the sum of square of two integral(Ex and Ey). I first hold this two integral because two variables(tx, ty) are not specified.Then, I replace tx,ty and releasehold ...
1
vote
2answers
83 views

How to force a replacement in an order that I want?

This is a follow-up to this question. I have a big sum, with lots of terms of the form ...
0
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0answers
57 views

How do I use Replace All? [duplicate]

I have an expression: a + b 2^(1/2) + (c + d 2^(1/2))*I I want to replace each occurrence of 2^(1/2) with ...
2
votes
1answer
70 views

Replacement producing unexpected result

If I use a replacement rule like ...
3
votes
1answer
33 views

TensorContract with KroneckerProduct instead of ordinary Times

Is it possible somehow to contract two tensors, say A={{a1,a2,a3},{a4,a5,a6}} and B={b1,b2,b3}, where the elements ...
9
votes
1answer
171 views

What kind of patterns in a list of rules would benefit from being Dispatched?

I have a long list of rules for manipulating expressions. They are of the form: ...
2
votes
1answer
120 views

Function not returning number [closed]

I am quite new to Mathematica and I guess this question is really basic, but I can't figure it out myself. I'm making a simple notebook that plots a Hamiltonian function, a plane of constant energy, ...
6
votes
4answers
615 views

How to replace a space by a comma

in this expression = "{1 2 3 4 5 6 7 8}", I want to replace each space by a comma , to get ...
0
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0answers
52 views

Can't operate on vector within a list of rules

I'm trying to set up a list of rules which includes the following: ...
0
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2answers
44 views

Unevaluated derivatives of known functions after replacement

I want to make the following replacement work correctly: Array[(2 D[xM[[#1]][t], t] * D[xM[[#2]][t], t]) &, {3, 3}] /. {xM -> {Sin[ω t], Cos[ω t], 0}} ...
0
votes
0answers
36 views

Replace function and its derivatives [duplicate]

When I have a complicated expression that depends on some variable, say, $f$, the following usually works ok: Expression ./ { f-> x^2 } But if $f$ is a ...
6
votes
3answers
861 views

Replacing Tan[x] with Sin[x]/Cos[x]

Why doesn't this work? (1 - Tan[x])/(Sin[x] - Cos[x]) /. Tan[x] -> Sin[x]/Cos[x] I get back: ...
11
votes
2answers
95 views

Replace and Association

I'm surprised that I can't find this question already, so perhaps I'm missing something obvious. I would like to take a list of associations and remove any with value ...
0
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1answer
43 views

Solving a trigonometric equation for all $x$ using constant coefficients

I want to find the coefficients $a$, $b$, $c$, etc. that make an equation like $a+bx=x$ true for all $x$, but for trigonometric functions of $x$. For example ...
4
votes
2answers
56 views

Composition of rules: a->b + b->c = a->c

I am trying to compose two rules to form a new one: {a -> b, b -> d} and {b -> c} should become ...
3
votes
1answer
66 views

Convert an expression to use a specific analytic form

I have an expression that evaluates to an expression containing multiple ExpIntegralEi expressions. However, I would prefer that Mathematica use ...
1
vote
1answer
39 views

Pattern matching for product of two terms fails if one factor is 1

I have a long set of replacement rules that I utilize to solve some longish integrals over trigonometric functions. Just look at this snippet (from this answer): ...
4
votes
2answers
134 views

ReplaceRepeated as a Looping construct?

There are a lot of discussions about looping constructs (notable example here). Wolfram language guides, as usually, contain most relevant links. Looping constructs guide has the following part on ...
0
votes
0answers
43 views

Replacing parts of a complicated expression with shorthand symbols

I have a list, each element of which contains a different complicated expression. Here is a simplified example of the first three entries of the list, displayed one above the other: $\frac{Ey \ \mu \ ...
2
votes
1answer
79 views

How to do literal replacement to format expression?

I can do a replacement of an expression with some variables to alternate symbols: ...
0
votes
1answer
50 views

Misunderstanding of Replace code

I am looking for the right way to replace $\delta \, \, \text{by} \, \, 0.05 \, \, \, \beta \, \, \, \text{by} \, \, \, 1.77 \, \, \, \text{and} \, \, \, n \, \, \, \text{by} \, \, \, 12$ in this ...
1
vote
2answers
117 views

Apply tranformation to particular list elements

I have a list with elements {a -> -1, b -> -2, c -> -3} If I now wanted to apply a tranformation to b and ...
3
votes
1answer
66 views

Is the replacement operator associative?

In mathematics, a given operation $\circ$ is said to be associative if there is equality $$(f\circ g)\circ h=f\circ(g\circ h)$$ for any $f$, $g$ and $h$. Intuitively, this means ...
5
votes
5answers
431 views

Random character change in a random place

I would like to ask for help in a Random Replace of character. For example: ORANGE and change 1 character randomly (random place and random character from ORANGE) in it into any character of ORANGE, ...
2
votes
1answer
56 views

Replacing elements in a list if contains X (string)

I want to replace T1 with T2 if the list contains X (It's a string with something more) or else return unevaluated. Input:...
0
votes
2answers
41 views

How to replace a hole mathematical expression? [closed]

I have the following function: Input: f=-a n^2/v^2 +v/n I want to Replace v/n by v_new ...
0
votes
1answer
127 views

Getting mathematica to factor out constants and apply euler's identity to a table

I'm doing some quantum mechanics homework that I'm going to eventually generalize to higher spin states, so the solutions are going to need to be decently independent of the dimensions of the table ...
7
votes
3answers
168 views

A replacement question

I have: {{θ -> 0}, {θ -> (2 π)/ 3}, {θ -> π}, {θ -> (4 π)/3}} I would like to create a list of points $(\cos\theta,\sin\theta)$ using each of the ...
4
votes
2answers
64 views

Type error before replacement rule is applied

When I type a <> "0" /. {a -> "1"} I get the error ...
2
votes
2answers
142 views

Replacement rule not having desired effect

So I have this replacement rule that tends to work in most cases, except occasionally in cases like this: ...
10
votes
4answers
201 views

Timing problem with ReplaceRepeated

I have the following data: ...
8
votes
1answer
81 views

On an existing notebook, how to transform all “double brackets” into “DoubleBracket”

Sometimes, having all double brackets [[...]] transformed into \\[LeftDoubleBracket] ... \\[RightDoubleBracket] can really ...
2
votes
1answer
58 views

Using strings in defining rules

I am very new using Mathematica and I would like to define a rule of replacement which operates as below, keeping freedom for what concern the pre-factors that can appear in the equation: $$e^{\pm ix} ...
1
vote
0answers
26 views

Why variable in SparseArray can't be replaced? [duplicate]

SparseArray[{1, 1} -> t] /. t -> 1 Still contains t. Why t is not replaced by 1?
14
votes
4answers
400 views

A replacement problem

list = {1, x, 3, x, 4, x, x, 3, 4, 3, x, 2, 3, x, 8, 7}; If there is exactly one integer between two x I want to replace it with y: ...
2
votes
1answer
71 views

how to change Symbol to other symbol?

I have Input =a**b**c I want to have output such as {a,b,c} So I want to change **->, but replace code does not work. How ...
2
votes
1answer
79 views

How to replace $-x^{}\,y^*-y^{}\,x^*$ by $-(x^{}\,y^*+y^{}\,x^*)$?

Up to now, I have tried some codes like the following: ...
0
votes
1answer
70 views

How to write an expression in the desired form?

I have the following code: ...
3
votes
1answer
84 views

How to insert into a nested list/association?

Considering following nested structure: ...
1
vote
1answer
112 views

why doesn't the replacement rule work?

I have the following code: ...
3
votes
1answer
77 views

Simplifying an expression with complex variables

The other day I was trying to simplify the following expression of $w \in \mathbb{C}$ and $|w| < 1$: $$f(w) = \left|\frac{2}{(\frac{w+1}{1-w}+1)^2}\right|^{-\Delta} \cdot \frac{1}{\left|{\rm ...