Questions tagged [replacement]
Questions about Mathematica's rule-based replacement functionality, including functions such as Rule (->), Replace, ReplaceAll (/.) and ReplaceRepeated (//.).
1,054
questions
0
votes
2answers
54 views
Simplifying polynomial in one variable by substitution
I want to simplify a polynomial in variable $x$ with integer coefficients by substitution $x\to{x}/d$ so that the coefficients become smallest possible integers.
Input:
...
2
votes
1answer
28 views
0
votes
0answers
32 views
Delayed Rule right-hand-side mis-evaluation
Outline
I am trying to create a rule that will give me a minus sign if the number of times A is applied on X is odd where A is some οperator and X a random quantity.
Some of the configurations of ...
1
vote
1answer
38 views
Filter out terms that include any combination of F[X] and G[-X]
I have the following problem which is closely linked to a previous question I asked some time ago (Replacement rule for terms that are separated by operators?).
In this specific instance, suppose I ...
0
votes
0answers
30 views
Rule Replacement Fails with Embedded Conditional
I was using a rule replacement that creates a matrix. At one rule, I added a conditional to return one vector and then added that (after the conditional and within the same replacement) to another. ...
1
vote
1answer
32 views
1
vote
0answers
34 views
The replacement function is an integral and the double integral yields a different answer than the normal double integral
I am fairly new to Mathematica. I have a quick inquiry. The code is simple and just 3 lines. Trying to do a replacement rule as follows
...
6
votes
1answer
84 views
ReplaceList Except Alternatives bug
Bug introduced in 11.3 or earlier and persisting through 12.0 or later
[CASE:4352435] and [CASE:4354378]
In Mathematica 11.3 and 12.0,
...
0
votes
1answer
29 views
Suppress arguments in output for pretty print [closed]
I would like to define a rule that suppress any arguments of a function for visibility.
I tried:
rule = f_[x__] -> f
While this works well with individual ...
2
votes
1answer
55 views
Handling a list of variable assignments to be used with `With` [duplicate]
Is there a way to use With as follows?
variables := {a = 2, b = 3};
With[variables, a^b]
Desired output
...
0
votes
0answers
35 views
making replacements when patterns don't match exactly
I want to simplified some mathematical expressions, and they are similar to
...
1
vote
1answer
46 views
TagSetDelayed for spotting zero derivatives
I am trying to implement my own differential operator, d[arg_, var_],
that computes the derivative of arg w.r.t. ...
0
votes
0answers
31 views
Tracing & Modifying a Function (Replace All) [duplicate]
For the function:
f[x_Plus] := Apply[Times, x]
f[a + b + c]
Out[]= abc
This is clear, as the Times is applied to the list with Plus head in f.
However, when ...
1
vote
2answers
35 views
Manipulation replacements rules from Solve [closed]
Assume the call to the routine Solve[eqn==0,{x1,x2}] returns:
{{x1->a1,x2->a2},{x1->b1,x2->b2}}
I would like to ...
0
votes
0answers
31 views
Replacing in FeynCalc
I started to take the trace of some terms in FeynCalc package. I encountered a problem in replacing. Here is my problem:
...
3
votes
3answers
59 views
Assign Values from Array to Array [duplicate]
I am trying to simply do the following
cVec = {a,b,c,d}
From another expression, I obtain another vector, say,
...
0
votes
0answers
25 views
Variable subscript substitution - easy way?
I have a Mathematica expression with about 900 terms, that looks roughly like this:
$X_{1,1} + Y_{1,2} + Z_{1,3} + XX_{1,4} + XY_{1,5} + ... $
Is it possible to perform a fast method to copy this ...
0
votes
0answers
35 views
Implementing a generic product rule
I'd like to implement a generic rule for expanding differential forms by the product rule. For instance, I'd like to transform the following PDE:
$\phi \frac{\partial \phi}{\partial t} = \phi \nabla^...
3
votes
1answer
35 views
Prevent argument substitution in held expression when injecting into unevaluated code
I want to write a custom sow/reap pair to wrap any piece of code in sow[code] and call reap ...
0
votes
0answers
47 views
Derivative operator w.r.t a vector index and change of variables
Description and code lines:
Define a scalar product to represent $A_i·A_j$ , $A_i ·B_j$ and $B_i ·B_j$, such that $A_i · A_i$ = 0.
This is implemented in the following way:
...
1
vote
0answers
35 views
ReplaceAll on a Plot - Can you reproduce this error?
The weird thing is that it occurs only the first time I evaluate it!
The same happens with Plot but not with Graphics.
I can ...
0
votes
1answer
24 views
Plot with substitution of domain values before evaluation of function
I have a function of two variables $f(x,y)$. I find the maximum value of $f(x_0,y)$ by first substituting the value of $x=x_0$ and then maximizing in the range $0<y<1$.
My question is: How to <...
4
votes
5answers
307 views
Applying rules on rules
So I tried taking a total derivative, with constants, but then the ouput had Dt[ ..., Constants -> ...] as an output. I tried to use a rule to remove it from tha output, but it did not work. See below....
0
votes
1answer
32 views
Retrieve the independent variables from a linear replacement list
Is there a good way to convert a linear replacement list into a list of the independent variables? For example, I would like to take {n1->n3+n4, n2->n3+2n4} and get {n3,n4}, the variables that n1 and ...
1
vote
1answer
54 views
I want $(t+x)^n$ to be replaced with $f(n,x)$ throughout expression, what should I do?
I want $(t+x)^n$ to be replaced with some function $f(n,x)$ throughout any expression, what should I do?
0
votes
0answers
48 views
Why is a certain replacement rule not succeeding?
I've been trying to apply the replacement rule
/. Sqrt[-(-1 + 2 l3) (2 - l3 + 2 Sqrt[1 - l3 - 2 l3^2])] -> (1 -
2 l3 + Sqrt[1 - l3 - 2 l3^2])
on certain ...
3
votes
2answers
73 views
ReplaceRepeated problem
I am driving myself nuts.
I have a list of data consisting of team number, team names and results from a tournamet (the results are called imps, vp, and cum).
{teamNumber1, teamName1, teamNumber2, ...
0
votes
1answer
57 views
What's wrong with this input? [closed]
Can anybody with all my gratitude tell what's wrong with the input in the attached file? why Mathematica doesn't return the answer?
Thanks in advanceHere is the Attached file
2
votes
2answers
57 views
How to split the expressions into four parts include the coefficients of Sin[x], Cos[x], and Exp[x], respectively?
Given three expressiones as
...
0
votes
0answers
37 views
ReplaceAll and complex numbers
I am currently trying to "canonicalize" my expressions with complex numbers. One thing I want to do is to replace expressions such as x x* (where * denotes complex ...
1
vote
1answer
61 views
How to get ReplaceAll to happen before function call
I have a problem I am attempting to solve with NMinimize.
I have a scoring function, which will give me a final score. The problem has many variables, so instead of having them as parameters, they ...
7
votes
3answers
138 views
How to replace $x$ and $x^2$ with different value?
I have an expression now
expr = x + x^2
what I want to do is to replace $x$ with $k\times p$ , and $x^2$ with $[k\times p + k\times(k - 1)\times p^2]$.
The ...
2
votes
2answers
54 views
Hiding variable names in function definitions
I have a problem where Table and similar functions' substitution variable name can conflict with names in my function it self. Here's a minimal example
...
0
votes
1answer
64 views
0
votes
0answers
32 views
1
vote
1answer
72 views
Variable substitution like usual maths
So... I'm trying to get some simplifications on equations using own defined variables, but the tries I gave didn't result on what I wanted.
The problem: I have 2 variables defined as:
...
2
votes
1answer
59 views
Replacement patterns
I wanted to ask if there was a way to quickly replace multiples of the same thing, instead of writing it so many times, for example:
...
2
votes
1answer
39 views
Replace sub-expressions matching a pattern unless located under specific heads
Suppose I have some rule, e.g. Re[x_] :> (x + Conjugate[x])/2. I want to apply it to all matching sub-expressions in some expression, excluding any sub-...
0
votes
0answers
25 views
Contracting the KroneckerDelta should bring it back
I would like to define a function
$$V[\phi] = \sum_{1\leq i,j,k,l\leq dim}\lambda_{ijkl} \phi_i\phi_j\phi_k\phi_l, $$
with $\lambda_{ijkl}$ defined by contractions of the type $\delta_{ij}\delta_{kl}$...
2
votes
2answers
118 views
Add a suffix to the end of every number in a string [duplicate]
I have some polynomial e.g. $2x^2 + 3x + 4$
In Mathematica I can define this, and convert it to a string simply enough
...
4
votes
3answers
66 views
All possible replacements of an expression, considering each term separately
Say I have an expression:
f[a, f[a, b]]
I would like to replace each a with either x or <...
2
votes
1answer
52 views
Replacement Help, Patterns, Rules?
I have been trying to replace multiples of one thing in an expression, for example:
(E^(4 s - 2 z) + E^(8 s - 4 z) + E^(12 s - 6 z)) //. {(4 s - 2 z) ->
meow}
However, I end up with the ...
3
votes
3answers
77 views
Identify complex expression and replace
I'm having trouble finding a way (if there is) to analyse an expression, identify a complex pattern in it and then replace it with another thing. I think it will be easier to explain my problem with ...
1
vote
1answer
40 views
Drop-down menu to globally change definition of a function `t[x]`?
If have a function t[x_] which is used extensively in a long notebook, but which has a variety of definitions, and which is used in a variety of ways. I'm looking ...
2
votes
3answers
86 views
Replacement rule with all possible permutations
I have a list with expressions like
{1,3,5,a,c,b,3,d}
I want to generate all outputs with permutations of {a,b,c,d},
so for example a rule like
...
0
votes
1answer
58 views
defining rule for derivative on arbitrary function
Is there a way in Mathematica for defining rules for derivatives on undefined functions? For example, I would like to define a rule such that for any function $f(x,y)$, when I take the $x$-derivative ...
3
votes
1answer
36 views
Replacement rules for partial derivatives
I have a system of PDEs, and it contains terms of the form $A^{(n,m)}(x,t)$, which is shorthand for $$\frac{\partial^n}{\partial x^n}\frac{\partial^m}{\partial t^m}A(x,t),$$ (ie ...
0
votes
0answers
53 views
How to use replace for only one term in a long expression in Mathematica?
I am doing some Cauchy integration and in some intermediate steps I have something that looks like that:
(..many_terms...+I*\epsilon(k1-p1))/k1
where ...
2
votes
1answer
44 views
How to construct multible rules for replacement at once?
After generating a list for which I used //N, I want to replace some values with the exact one.
What I had in mind is to generate something like:
...
7
votes
1answer
217 views
A “Replace” sort problem. Basic but haunts me
Here's my problem when doing my codes.
I need an output similar to {{p->1},{p->2},{p->3},{p->4}},where p is a ...
