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

learn more… | top users | synonyms (4)

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 ...
8
votes
0answers
148 views
3
votes
0answers
84 views
3
votes
0answers
120 views

Define (conditional) substitution rule for sum/difference of radicals

I want to tell Mathematica to simplify some expressions applying the following substitutions, conditioned on the fact that $a\geq 0,b \geq 0, a^2-b\geq0 $ $$ \sqrt{a+\sqrt{a^2-b}} \pm ...
2
votes
0answers
37 views

Replacement rule for summation with Kronecker delta

I want to perform some symbolic computations in index notation, without explicit reference to sums, so that in expressions of the type f[i,j]g[j,k] summation over ...
2
votes
0answers
133 views

Is this a bug in NCAlgebra library?

In course of my work with NCAlgebra package for Mathematica, http://math.ucsd.edu/~ncalg/ , I encountered unexpected behavior of replacements. I am using ...
1
vote
0answers
35 views

Pretty equations in HoldForm[]

I have been generating equations programmatically, resulting in lists that look like this: {Log[2,(4^4)^3, 3 (Mod[2,4] 4), Log[root[2, 3], 4^4]} where ...
1
vote
0answers
155 views

A faster way to replace variables than ReplaceAll

I noticed that for large matrix, the rule /. is very slow. In the example below, the combination of memorization and the replacement "/.sol[n-1]" inside the definition of sol[n] turns the code ...
1
vote
0answers
141 views

Replace part of a matrix

I have to generate a ne numbers of matrices with 1 and 0 and then replace some elements. ...
1
vote
0answers
135 views

Speed up replacement using Rule Dispatch Associtation

I knew that this has asked many times, but I hope there is something more could be done to speed this up. The expression kappa is here. ...
1
vote
0answers
148 views

Replace part in a matrix that matches specific pattern

I have the following problem. Given a matrix L which looks as follows, Matrix L is a link, route matrix. Further, I got the following vector (d), which indicates the demand per vertex combination. ...
1
vote
0answers
63 views

Hashing by Equals instead of SameQ

I have some numerical code involving complex numbers representing points on a plane. Some of these are equal but not identical, ie ...
1
vote
0answers
53 views

How to apply an rule to factors matching a certain form

Suppose we have many expressions involving irrational ArcTan expressions (such as ArcTan[Sqrt[3],5]) along with other irrational factors (such as ...
1
vote
0answers
84 views

How to simplify expressions

I read several similar posts but I have not found a solution yet. However, I think that my problem should be quite easy. So here we are. Relations ...
1
vote
0answers
213 views

Variable scope in nested NMaximize, NMaxValue

I'm trying to use NMaxValue inside other statements (FindRoot and NMinimize). Those statements should bind variable names, but I'm getting weird warnings which seem to indicate that the variables ...
0
votes
0answers
41 views

Using ParametricPlot to Display result of Maximize

One would expect that: Plot[f[x],{x,0,1/2}] and ParametricPlot[{x,f[x]},{x,0,1/2}] would always yield identical outputs. ...
0
votes
0answers
24 views

Symmetric properties of KroneckerDelta under replacement

The consider the following code: ...
0
votes
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
votes
0answers
42 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 \ ...
0
votes
0answers
91 views

Replacing function in Sum

I have this expression, which, after execution, gives these $F[s,r]$ in output. $$ S_{1,1}=\sum _{s=1}^{16} \sum _{r=1}^{16} F(s,r) \text{Tr}\left[G_r.G_1.G_s.G_1\right] $$ Here is a piece of ...
0
votes
0answers
52 views

Mathematical symbol and name for Symbolic Replacement

(Originally from math.SE, but might be better here) I'm searching for a mathematical symbol, that describes the symbolic replacement done for instance in Mathematica: ...
0
votes
0answers
71 views

Matrix iteration failing after second step

I am calculating 11x6 matrix using different logics as in below code. Problem is in Do loop in below code where I have two different criteria to update matrix "fd". I am expecting logic in IF which ...
0
votes
0answers
84 views

Creating a lazy evaluator of the lambda calculus

I have a sub project in my research to write a lazy evaluator of the lambda calculus. How should I approach this problem? I already have a implementation of the lambda calculus in another language. ...
0
votes
0answers
273 views

Writing rules for Einstein summation

I'm trying to write a list of rules for tensor manipulations and in particular, Einstein summation convention. What I've tried, so far is to write something that would take a generic functions with ...
0
votes
0answers
188 views

Back Linear Substitution

I have an equation set Ax=b and A(n*m),n<m . To lower down the dimension, I express some vars by other vars, which gives ...
0
votes
0answers
237 views

Alternate method of conjugation using replaceall

Mathematica really struggles to simplify complex conjugates of complicated expressions - even given assumptions for every symbol in the expression being real. Often times I've found that I can ...