Questions tagged [expression-manipulation]

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

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14
votes
1answer
756 views

How to convert a notebook cell to a string retaining all formatting, colorization of identifiers etc?

I have an opened Mathematica notebook containing several cells. Suppose, I am interested in one of them -- it may contain a complete or incomplete expression (e.g. with syntax errors, highlighted ...
13
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2answers
877 views

How to embed an image into a string?

Note: The bug described in the post is in Mathematica 9, and has been fixed in 10.0. The documentation for String contains the following statements: Strings can ...
15
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3answers
712 views
8
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2answers
1k views

How to add equations' left and right sides together?

If we have two equations E1 and E2, and instead of using Solve to solve it, we simply need to manually add them up which would allow some simplification that could ...
5
votes
1answer
602 views

How to decompose a complex expression containing repeated subexpressions? [duplicate]

Suppose I have an expression like ...
1
vote
1answer
2k views

How can I get Mathematica to write Log instead of ArcTan?

ArcTan really bothers me, so is there a way to make Mathematica write Logarithm instead of ...
9
votes
4answers
997 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 ...
3
votes
1answer
260 views

Indexing of Large Autonomous System of Equations for Use in NDSolve

I currently have a list of ~150 autonomous ODE's that I need to be able to work with using NDSolve. Fortunately I already have them formatted in plaintext, which ...
2
votes
3answers
362 views

Symbolic manipulation of functional form

I have a functional polynomial expression of the form: ...
2
votes
1answer
243 views

Examine function parameters programmatically

I write a lot of scripts in Mathematica and I'd like to eliminate the boilerplate that parses command-line arguments and assigns them to variables of the correct type before doing the real work. I was ...
22
votes
3answers
1k 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 ...
1
vote
1answer
594 views

How to extract the coefficient from an expression

Here is the expression. I want to extract the coefficient just as the table showing below. I can do it by hand, but I expect a code that can automatically identify how many differenct terms there ...
1
vote
1answer
204 views

Trying to show an expression is always zero

I have a symbolic matrix $$m = \begin{pmatrix}A1 & B1 & C1\\A2 & B2 & C2 \\ A3 & B3 & C3\end{pmatrix}$$ and I believe that Det[m] is ...
18
votes
1answer
494 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 <...
2
votes
2answers
2k views

Dropping Higher Order Terms in symbolic evaluation

I have a series of symbolic manipulations (along with some coefficients). As a sample, here is one of the intermediate forms ...
5
votes
2answers
533 views

Match and replace subexpression

I would like to replace the expresion $(n1-1)$ to $z1$ in following: 2*n1*p[n1-1,n2] 2*(z1+1)*p[z1,n2] I have tried Replace...
1
vote
2answers
2k views

How can I prevent Mathematica from evaluating or “simplifying” an expression?

Simple example: ...
2
votes
2answers
305 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, ...
24
votes
5answers
5k 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: ...
4
votes
1answer
2k 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 ...
6
votes
2answers
861 views

How to get the matrix coefficient from a QuadraticForm expression in a very fast way?

As we know, QuadraticFormDistribution is the distribution of z.a.z + b.z + c for a real-valued p x p symmetric positive definite ...
19
votes
1answer
865 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 ...
33
votes
8answers
2k 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?
6
votes
1answer
2k 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
2answers
499 views

How can I retrieve the point coordinates from a LOG Plot after the data points were manually moved?

I'm having problems with getting coordinates out ofa ListLogLogPlot I basically plotted a list, then selected data points on the graph, moved these points around, ...
1
vote
1answer
756 views

Graph and manipulate DSolve result

Given a DSolve example: ...
11
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3answers
1k 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: ...
43
votes
3answers
23k views

How to change plot style or other options after it was created

For example: p = Plot[Sin[x], {x, 0, 1}] Is it possible to write options in Show to change the curve's color for example into ...
10
votes
2answers
4k 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 ...
2
votes
3answers
1k views

how to extract some terms out from an expression

I have an expression as below: $-\frac{1}{2} A[a,v] A[b,h] A[c,v] A[d,h] \text{Cos}[\theta ]^2+\frac{1}{2} A[a,h] A[b,v] A[c,v] A[d,h] \text{Cos}[\theta ]^2+\frac{1}{2} A[a,v] A[b,h] A[c,h] A[d,v] \...
18
votes
1answer
500 views

What are the default TransformationFunctions used in Simplify and FullSimplify?

If I do Simplify[(c^3 - s^3)^2 - (s^3 + c^3)^2, TransformationFunctions -> Automatic] (i.e. a verbose version of default behaviour), what transformation ...
7
votes
3answers
468 views

Threading Distribute[]

I wish to use Distribute[p.(q+r)+m] to get p.q+p.r+m. However, Distribute apparently does not thread through all parts of the ...
21
votes
1answer
653 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 ...
9
votes
2answers
7k 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 ...
14
votes
3answers
2k views

How to manipulate gauge theory in Mathematica?

I want to know if there is a way of typing into Mathematica an expression like the following, $$\epsilon^{\mu \nu \lambda} f^{abc} A^a_\mu A^b_\nu A^c_\lambda + g\epsilon^{\mu \nu \lambda} A^a_\mu \...
2
votes
1answer
1k views

Comparing two symbolic expressions

Does Mathematica provide any way to compare two symbolic expressions and find which is the greatest? For example, I want to find which is the greatest of ...
13
votes
6answers
375 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 ...
2
votes
1answer
559 views

Can mathematica simplify an expression setting simplified answer equal to zero?

Basically I want to reduce something like: Subscript[P, 4] - Subscript[P, 5] == Subscript[R, 4, 5]* Subscript[i, 4, 5] when only one of them is known (...
5
votes
0answers
231 views

Why doesn't Log[Gamma[]] simplify to LogGamma[] where it could?

I have been playing with various equations involving amount of permutations in relatively large sets. Easiest way to look at these is something like Log[10, bignumber!] . Often expressions, even ...
17
votes
2answers
802 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. ...
3
votes
1answer
285 views

Change values in equation with slider

I want to make an equation where the values adjust to my slider which I inserted with manipulate. Well, I tried, but when I use the slider the equation starts to fall apart. Actually this should ...
3
votes
2answers
161 views

Subvalue and level

I'm interested in the arguments of f in expressions like f[a]@f[b]@f[c] By argument I mean what is here ...
2
votes
1answer
216 views

How to prevent substitution?

I have a function: $\bar{u}:=u[t,x,y,z]$ (1) How do I prevent it from expanding and substituting in instructions like those following: $\partial _t {\bar u}$ (2) Thanks in advance EDIT: ...
2
votes
3answers
497 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 range) ...
13
votes
2answers
999 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 ...
13
votes
2answers
1k 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, ...
19
votes
3answers
1k 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 ...
10
votes
4answers
757 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 ...
52
votes
2answers
2k 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 ...
91
votes
4answers
4k views

Replacement inside held expression

I wish to make a replacement inside a held expression: f[x_Real] := x^2; Hold[{2., 3.}] /. n_Real :> f[n] The desired output is ...

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