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

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2
votes
2answers
186 views

Matrix exponential via Cayley-Hamilton Theorem

I'm attempting to calculate the exponential of a matrix via Cayley-Hamilton theorem. (Following the "concrete example" from http://en.wikipedia.org/wiki/Cayley%E2%80%93Hamilton_theorem) I am having ...
2
votes
3answers
228 views

How to manipulate log arguments?

A common problem I have with Mathematica is needing to manipulate the arguments of logarithms. Typically, I need to take ratios of the log arguments Mathematica gives me by default. That's to say ...
2
votes
2answers
447 views

Replacing values of a function

I have recently starting using Mathematica and have recently come to what seems as an impasse in my understanding of the language. If this is too "tell me how to do it" I would certainly understand. ...
2
votes
4answers
245 views

Extracting RHS from Rule

In an example from another question, the rhs of a list of rules can be simply extracted: ...
2
votes
3answers
380 views

How to manipulate nested expressions?

I have the following expression, only slightly complicated, and I'd like to do two things: Plot the elements of the lists (though messy, all are in the same ...
2
votes
3answers
183 views

What is the order of faces on a D20? How can I optimize the order of faces on a D-n?

I am creating a customizable D20 for 3D printing using OpenSCAD, with the following code: ...
2
votes
3answers
165 views

Simplify system functions

Consider the code defining two constants: a=Cos[t] b=Sin[t] Suppose that we have another value in terms of Cos[t] and ...
2
votes
2answers
115 views

Converting a date to a calendar quarter

I have a list that includes dates. I need to convert each date to be the last day of the quarter that it's in. So for example I want {2013,7,1,0,0,0} to become {2013,9,30,0,0,0}. Actually I don't ...
2
votes
1answer
109 views

Confused behavior using Dispatch to sort one list relative to another

I have a need to sort the entries of one list into the same sequence as the entries in a reference list. Because I have rather large lists involving strings, I'm trying to use Dispatch to accomplish ...
2
votes
1answer
65 views

Return the incomming expression on false

when I have an expression, that is unknown to mathematica, it is returned exactly the same, as it was called. For example SeeFlyingPigs[1,2] called on the line ...
2
votes
2answers
65 views

Conditional replace of a column

Im trying to replace the value in the Nth column of a list if a condition is true, returning the modified list. I've tried modifying the answer from 61219 and been through most of related questions ...
2
votes
2answers
129 views

Looking for an elegant way to solve a (system of) ODEs/functional equations with undetermined coefficients

I want to solve an ODE using undetermined coefficients/guess-and-verify and am looking for an elegant way to use this technique. I am running into a few ugly warts. Here is a basic implementation for ...
2
votes
4answers
174 views

Replacing High Densities of 1.s in Very Large Binary Arrays

I am working with very large binary arrays on the order of {100,100000}. It may look something like this. ...
2
votes
1answer
78 views

ReplaceAll in an expression including large InterpolatingFunction

I have a large InterpolatingFunction that I'm transforming to another basis with a few simple multiplications and additions by (symbolic) constants. The ...
2
votes
2answers
137 views

How to plot complex values given by Solve

Update Solve[N[Table[BernoulliB[n, z], {n, 10, 10}] == 0]] ...
2
votes
1answer
168 views

Add Pattern to List Removing Duplicates

Lets say I have a list of patterns ...
2
votes
2answers
115 views

Using a predicate to control the application of a rule in a replacement

How can I make a replacement rule that will only be applied to those parts of an expression that will not break a condition placed on the whole expression? For example, suppose I have ...
2
votes
2answers
176 views

Modify a sub-part of a sub-list only

I have this list: a = {{{0, 0}, {1, 7}, {2, 0}, {3, 2}, {4, 7}}, {{0, 0}, {1, 0}, {2, 1}, {3, 2}, {4, 7}}} and I'd like to transform it to this: ...
2
votes
1answer
103 views

How to program a clickPanel for chemical elements (like a periodic table)?

The command ColorData["Atoms", "Panel"] indicates RGBColors of "Atoms" by clicking a panel. As I don't want to reinvent the wheel, I asked myself: How to ...
2
votes
1answer
85 views

Table with some editable cells

I have a table: I want it to be editable only where the zeros appear. I read this post Generating an editable table that can be used as input because it's almost exactly what I want, but I couln't ...
2
votes
1answer
80 views

Using Total on a list supplied by a rule

I'm confused as to why Total complains about a nonatomic expression here: ...
2
votes
1answer
122 views

Applying rules to rewrite expressions that contain patterns

I'm trying to write a rule that can rewrite a pattern that exists in another expression. For some reason, this is proving to be more challenging than I expected ... most likely because I'm not totally ...
2
votes
1answer
153 views

Derivation after substitution not working

I have a code that will output an expression in form of a functions like this ...
2
votes
1answer
115 views

Replace an expression with a slightly tricky LHS transformation

I would like to make the substitution x^(11*y) -> r in the following equation x^(11 *y^z) - 1 to end up with: ...
2
votes
1answer
68 views

Unique[] in RHS of rule

I have a function, explicit that takes dot product of two symbols, and replaces it with repeated dummy indices generated by ...
2
votes
1answer
208 views

A Sierpinski-ish structure, via 2D automata

The project is originally based on a puzzle proposed by EIORU at http://www.ptt.cc/bbs/puzzle/M.1342451949.A.00F.html (若您懂得讀中文 / if anyone happen to read Chinese^^) last July. The descriptions, ...
2
votes
1answer
39 views

Substitution breaking the scope

A novice's problem, perhaps: it seems that /. substitution does weird things to the scope. ...
2
votes
2answers
36 views

replace an interval of values [duplicate]

I want to replace values in an interval [a,b] by 0 in a list of values. Example: {{.5,.2,.49,1,1},{.49,.5,.495,1}} I want to get: ...
2
votes
3answers
71 views

How to get an element of a list , which is computed out of substituted variables?

What is the best way to get the element of a list, which is computed out of substituded variables? For example one wants to get the first element of the first row of ...
2
votes
1answer
66 views

Add to the last digit a number

I have data from a Multimeter that has a precision of 0.6%rdg+4dgt. So i want to take the last digit of, say, 12.007 and add 4 to the last digit like ...
2
votes
2answers
69 views

Pattern evaluation in nested function call

I'll put the question right here, but will add some context below in case someone wonders why the heck I'm trying to do this. Why is it that I have to do two passes to get the value of the arguments ...
2
votes
1answer
74 views

Ordering for Pattern matching in Subscripts

I have some transformation rules acting on subscripted variables. When I match the a product the order matters. ...
2
votes
2answers
215 views

Applying rules with functions to expressions with derivatives

I have a function that I want to see applied, potentially within a derivative. The use of delayed vs. non-delayed rules seems irrelevant. See the following: ...
2
votes
1answer
94 views

Replace inverse function

I'm solving an expression like so: Solve[u[x] == u[a] + u[b], x] Mathematica returns {{x->(u^(-1))[u[a]+u[b]]}} If I ...
2
votes
2answers
409 views

Mass Symbolic Manipulation with Subscripts? (from plaintext Input)

The simplest example of the change being sought is a greek letter, typed in as plaintext nu, and its may be replaced by the symbol, ν: expr = 3nu*kx*ky+ ...
2
votes
2answers
89 views

Derivative of Vectoral NDSolve Interpolated Function / Rule Solutions,/., and Vector NDSolve [duplicate]

I need to find the instantaneous phase and instantaneous frequency for a rotating system. I am having difficulty making the math work with interpolating functions. First, here is a problem without ...
2
votes
2answers
158 views

Generating an editable table that can be used as input

Say I have a number $n_{max}$. I want a command to generate a table like 1 1 2 2 3 3 4 4 ... nmax nmax where the second column is editable, and this table can be ...
2
votes
1answer
83 views

Convert Integer to Numeric with Replacement rules

I have a long list of triples, each looking something like {AGO, 1988, 2345.23}. Some of these, however, have an integer in the third spot, like this: ...
2
votes
1answer
143 views

Strange behavior when replacing variables by numerical values [duplicate]

I have a rather complicated function with parameters {a, b, c, d, e, f, k}, and I'd like to know its behavior as a function of k alone given other parameters, so I try the following code: ...
2
votes
1answer
133 views

How to transform an expression using algebraical instead of pattern rules [duplicate]

I would like to transform rules algebraically. A very simple example would be: - k^2 - 2 k x + x^2 /. {2*k -> 1} This transforms to: - $$k^2-2 k x+x^2$$ ...
2
votes
1answer
117 views

replace RHS of rule

is there an elegant way of replacing the RHS of a rule with the value of some function of it. Say I have {{a -> 1.2}, {a -> 2.3}} and I want to replace ...
2
votes
1answer
147 views

#[[1]]//FullForm = 1?

I have a set of symbolic algebraic expressions that I'm trying to get some speed into. To illustrate the issue, I'll use a simple form like { k0 X, k1 Y, k1 Z}, ...
2
votes
0answers
54 views

Drop all powers from multinomial [closed]

How to automatically replace an expression like x^3 y + x y z^2 by x y + xyz in Mathematica, i.e. replace all ...
2
votes
0answers
94 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 ...
2
votes
0answers
106 views

Generalization of a rule to N arguments

I am trying to apply a series expansion on a function x[t1,t2,...tn], with an expansion parameter a. For ...
1
vote
4answers
199 views

How to find all symbols in an expression and perform an operation on them?

========== motivation =========== Suppose, for example, I have an incoming expression like m = (3-I)x + 4(x y)/(Cos[y]) I want to find all the symbols in ...
1
vote
1answer
134 views

Simple rule appears not to work

I have the following simple code ...
1
vote
2answers
70 views

Replacing a specific pattern of values at level 2 in a list

I've a list of lists, tl = {{True, False, m12}, {False, m22, m33}, {m32, False, True}} and each nested list has the same length, What is the proper way to ...
1
vote
3answers
127 views

Replace inside a Held expression separate context

How do I replace content inside a Held expression without local values coming through? For example if you run the following code you get g[2] instead of ...