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

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0
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0answers
62 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
45 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
37 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
936 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
101 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
votes
1answer
48 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
63 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
69 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
43 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
139 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
45 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
80 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
71 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
447 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
61 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
43 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
143 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
66 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
202 views

Timing problem with ReplaceRepeated

I have the following data: ...
8
votes
1answer
85 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
60 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
28 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
405 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
85 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
80 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
73 views

How to write an expression in the desired form?

I have the following code: ...
3
votes
1answer
89 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
94 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 Re}(\...
7
votes
1answer
190 views

Remove leading and trailing zeros from a list

This functions and gives the desired result: {1, 0, 2, 0, 0} /. {x___, 0 ...} :> {x} {1, 0, 2} But with leading zeros it doesn't: ...
1
vote
0answers
47 views

Collect fails to collect all powers of my variable [closed]

I am fairly new to mathematica and have not used it to really code anything at all, but just used it as an kind of advanced calculator. My issue is the following: I need to extract the power of a ...
3
votes
1answer
96 views

How could I perform this replacement?

I essentially have something of the form pm[1, 2] pm[3, 4] pm[5, 6] c[{1, 2, 5, 6}, "+"] c[{3, 4}, "-"] I want to add next to each pm a corresponding plus or ...
1
vote
2answers
172 views

Find the explicit solution of the integral

I want to calculate the integral: assuming that we are familiar with the relation: The answer should be: The code that I've used is the following: ...
5
votes
5answers
214 views

Converting set of characters into numbers using list of replacement rules

I am trying to convert a text, as an example "aaaa" into a set of numbers as defined in a list of replacement rules, for example letterstonum . letterstonum takes in letters a to z and returns the ...
1
vote
0answers
59 views

How can I perform this replacement? [closed]

I want to take an expression of the form p[1,2]p[3,4] and have an output of something like {{1,2},{3,4}} If I do the ...
2
votes
1answer
113 views
0
votes
1answer
53 views

How to do this replacement without a for loop?

I'm new to Mathematica and I'm trying to get past my desire to use For loops for everything; can somebody tell me a simple way to make this replacement? I want my input to be ...
9
votes
1answer
108 views

MapAt with Replace(All) causing kernel crash

Bug introduced in 10.1 and fixed in 10.2 I wanted to roll a function that works like /. but only acts on the very first match it encounters. ...
5
votes
1answer
86 views

How to transform abstract finite group to permutation group?

It seems that Mathematica only has group functionality for permutation groups? Then there is a step to transform the abstract finite one to a permutation one. As an example, consider the following ...
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 ...
5
votes
3answers
182 views

How to change symbols in differential equation with a single rule?

Problem Suppose I have a differential equation such as $\qquad f'(x)+f(x)=0$ and I want to change it into $\qquad y'+y=0$ My Method Using rule = f[x] -> y,...
5
votes
3answers
186 views

How to replace an element in a list with an element in another list with matching indices

I have a list like this l = {1 + 2*s, 2 + 3*s, 4 + 1*s}, and I have calculated s = {1, 2, 3}. I need to replace ...
2
votes
1answer
96 views

How avoid error message with Range?

Evaluating Range[1, n] /. n -> 3 produces an error message ...
0
votes
2answers
186 views

Approximate UnitStep for use in Enterprise CDF

The following Manipulate code displays the VectorPlot for all functions. (This code is a subset of a more extensive notebook which is based on the structure you see below. Consequently, I need to ...
1
vote
1answer
238 views

Duplicate Mathematica functionality in Mathematica clone or lisp [closed]

What is the easiest way to accomplish the following in a Mathematica clone or in any version of Lisp? Also it doesn't appear in any lisps have a similar replace function. ...
0
votes
1answer
33 views

Substitute ratios

Suppose that I have the expression (x+y+z)/y. I want to substitute the rules Phix -> x/y, Phiz ->z/y. Is there a way to ...