How to manipulate expressions structurally, not necessarily complying with the rules of algebra.

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33
votes
3answers
602 views

Replace inside Held expression

I wish to make functional replacement inside Held expression like this: ...
40
votes
2answers
1k views

Head and everything except Head?

I have been working on picking expressions apart using Head and Part and encountered a little mystery. Consider the canonical ...
4
votes
1answer
412 views

Behavior of expression evaluation in Plot

I'm confused with Mathematica's way of parsing expressions. I've been struggling with this for a while and never found an exhaustive answer, sometimes things don't parse the way I think they would ...
5
votes
5answers
152 views

Is there an analogue of the Variables command for general expressions?

The command Variables[poly] gives me a list of all variables that appear in the expression poly, which involved sums, ...
14
votes
3answers
432 views

Comparing Mathematica expressions like diff

I am looking for a way to compare (or "diff") two Mathematica expressions, similarly to how to diff utility can compare two text files and report the differences. Has anyone already written such a ...
13
votes
1answer
352 views

Transform an expression into a graph that can be plotted with TreeGraph (not TreeForm)

I would like to plot an expression (like TreeForm does), but using the new TreeGraph functionality. ...
9
votes
3answers
591 views

Pattern matching a pattern with patterns

Confusing title, I know. But the question is, if we have two patterns which have the same general structure but different names used in the patterns and different names: ...
16
votes
1answer
434 views

List manipulation to build a functional expression

Since Mathematica deals with Head[a, b] as an expression in this way The first Part of Head[a, b] is ...
11
votes
2answers
552 views

Displaying a series obtained by evaluating a Taylor series

Description of problem I would like to use Mathematica to display the series obtained by substituting a value for $x$ in a Taylor series expansion. The terms of the series will be rational numbers, ...
17
votes
3answers
523 views

How can I completely ban usage of some functions in output and mandate use of others?

For example, I hate that Mathematica uses Pochhammer symbol in outputs and prefer all the expressions in Gamma function. How can ...
7
votes
4answers
305 views

Counting multiplications (complexity function)

I'm trying to count the number of times multiplication appears in an expression (for the purpose of constructing a ComplexityFunction that would help me simplify a terrible algebraic expression for ...
21
votes
7answers
846 views

How do I get my equation to have the form $(x-a)^2 + (y-b)^2 + (z-c)^2-d = 0$?

I want Mathematica to express the equation $$-11 - 2 x + x^2 - 4 y + y^2 - 6 z + z^2=0$$ in the form $$(x - 1)^2 + (y - 2)^2 + (z - 3)^2 - 25=0$$ How do I tell Mathematica to do that?
7
votes
4answers
538 views

Extracting variables from an expression

I'm looking for a way to extract a list of variables from an expression, for example with an input like: ...
9
votes
2answers
3k views

How to expand tan(x+y) as normal form?

TrigExpand@Tan[x + y] gives $\frac{\sin (x) \cos (y)}{\cos (x) \cos (y)-\sin (x) \sin (y)}+\frac{\cos (x) \sin(y)}{\cos (x) \cos (y)-\sin (x) \sin (y)}$ but I ...
8
votes
1answer
713 views

How do I expand a sum?

I have a problem with Mathematica's symbolic manipulations. As an example, consider the following expression: $$\sum _{i=1}^n -2 x_i \left(-a x_i-b+y_i\right)=0$$ How do I get Mathematica to expand ...
1
vote
3answers
166 views

Conjugating symbolic expression

I am trying to conjugate a symbolic expression, and I have explicitly stated the real terms. However, I simply can't get it to work: ...
13
votes
2answers
382 views

How to embed an image into a string?

The documentation for String contains the following statements: Strings can contain any sequence of ordinary and special characters: … Strings preserve ...
10
votes
1answer
224 views

Why is ReplaceAll behaving like this?

I'm learning to use the ReplaceAll function and I found the behavior of which is quite confusing. For Sqrt[f[x, y]] /. f[___] -> u Mathematica returns ...
7
votes
3answers
319 views

How to extract expression from ConditionalExpression

p1 := y /. {First[Solve[x^2 + y^2 + x == 1, y, Reals]]} ...
6
votes
1answer
200 views

Summa package problem

I need to use the features of the Summa package but it doesn't work in Mathematica 9. It gives the error Cannot open Utilities`FilterOptions` My question is: ...
2
votes
2answers
144 views

How to change the Integer to a special form in an expression?

I have an expression. I want to change all the Integers to a new form. The rule is, x_Integer->x._f. But we should consider some special cases. For example, ...
20
votes
1answer
301 views

How can I see which transformations Simplify attempts?

The documentation for Simplify[expr] says that it performs a sequence of algebraic and other transformations on expr, and returns the simplest form it finds. How can I see which transformations it ...
10
votes
3answers
660 views

How can I transfer mathematical expressions between Mathematica and Maple?

Is there a simple way to copy mathematical expressions between Mathematica and Maple (or at least in one direction)? I mean only expressions built from numbers and predefined mathematical functions, ...
11
votes
5answers
250 views

Construct an infix operation from a list

Inspired by this question, if I have a list {a, p, b, q, c} where p and q are binary ...
11
votes
2answers
566 views

Google Code Jam: Mountain View code review

After participating in Google Code Jam 2012 Round 2, it occurred to me that the Mountain View problem boiled down to solving a set of linear inequalities, which could be done in Mathematica. I've only ...
9
votes
1answer
120 views

What are the scoping rules for function parameters shadowing System` symbols?

Here are some very contrived code snippets, highly unlikely to appear in real code, but still I am curious why they behave like this: ...
6
votes
0answers
132 views

Using FunctionExpand to evaluate symbolic derivatives

Some symbolic derivatives of certain special function are not expanded automatically, but FunctionExpand often helps to get a derivative-free closed form ...
11
votes
3answers
184 views

How to collect expressions from cells created by Print?

I have a notebook where evaluation of a certain cell produced hundreds of adjacent output cells using Print. I need to create a list containing all expressions from ...
5
votes
2answers
178 views

Passing list of options to Plot

I'm looking for a way to create a variable that I can use to hold all of the graphics directives for, say, a plot command. For example, I have 8 plots with variations on the following: ...
3
votes
2answers
233 views

Simplifying expressions involving Sum

I am trying to use Mathematica to simplify a symbolic expression involving Sum. Particularly, I define a sum via ...
10
votes
4answers
398 views

Extracting equations from Piecewise expressions

Say I have a PDF: PDF[LogNormalDistribution[1.75, 0.65], x] Calculating it, Mathematica gives me an expression that looks like this: I want to extract the ...
4
votes
2answers
149 views

Getting a usable expression tree

I need to get the expression tree for some expression. expr //TreeForm The above grabs the expression tree but it isn't in some sort of usable format. Just an ...
2
votes
1answer
145 views

Indexing of Large Autonomous System of Equations for Use in NDSolve

I currently have a list of ~150 autonomous DAE's (differential-algebraic equations) that I need to be able to work with using NDSolve. Fortunately I already have ...
2
votes
1answer
505 views

Variable name string to expression

I'm not sure how to name this problem appropriately. But anyway. I have, say, three variables (arrays in my case), which I call: A1, A2, A3 I would like to ...
1
vote
2answers
266 views