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

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4
votes
1answer
69 views

Returning all branches of a multiple-valued function

This question and answer was inspired by this closed as duplicate question. One possible definition of the n-th order root of x ...
6
votes
2answers
209 views

ReplaceAll problem

Bug introduced in 10.1 and persisting through 10.2 or later Confirmed, as bug, by WRI: [CASE:3402234] I am trying to combine terms of the type ...
21
votes
2answers
635 views

Given an exact formula, how can Mathematica find a probability distribution whose PDF matches it?

So, given some data, Mathematica 10.2 can now attempt to figure out what probability distribution might have produced it. Cool! But suppose that, instead of having data, we have something that is in ...
0
votes
1answer
66 views

Extract all elements of an expression in order into a list [closed]

I have and expression a + b + c - d and I would like to generate a list of {a, +, b, +, c, -, d}. I have tried ...
4
votes
5answers
115 views

Assigning the numerical results of Minimize to variables [closed]

I need to use the numerical values returned by Minimize in further computations. Consider, ...
0
votes
0answers
108 views

More simplification tricks in Mathematica? [duplicate]

I need to simplify the following expression in order to operate on it using InverseLaplaceTransform. This result will be used in further work, so ideally I would ...
3
votes
1answer
137 views

Separating exponential terms

Suppose I have a lot of expressions multiplied by factors such as: $$e^{-i\theta[1]-i\theta[2] - i\theta[3]-i\theta[4]-i\theta[5]}$$ I would like to separate this into a product of exponentials of ...
13
votes
1answer
244 views

ToExpression processing errors

Is their a way to get a more comprehensive return value when running ToExpression? For example when I run ...
2
votes
1answer
145 views

Select largest number using pattern

I have the following expression: myExpr=R[C[2],B].(II+R[C[3],C[2]].(II+R[C[4],C[3]])) I need to create a pattern which would replace the ...
-1
votes
4answers
104 views

Converting an expression to function [duplicate]

I have the following problem. I current can automatically create the variable positionPayload, for instance: ...
2
votes
0answers
70 views

Derivative of vector dot product with respect to a vector

I have the expression: Transpose[gvecI, {2, 1}].x (m[1] + m[2]) gvecI and x are [3x1] ...
2
votes
1answer
99 views

Simplifying Expressions for FindMinimum

I am currently trying to apply the FindMinimum function to find the lowest energy of an expression. My current expression as of now is relatively complicated. It is the summation of 48 similar terms, ...
-1
votes
1answer
50 views

Position not working? [closed]

I have the list: myList={0,0,0,a,b,c,0,0,d} I need to find the positions of all elements that are non-zero. I do like this: ...
3
votes
2answers
82 views

Find sub-sets of vanishing additions or subtractions from a list?

Let's say I have a list L containing n numerical numbers. Now I want to find all sub-sets of ...
2
votes
1answer
62 views

Dropping rational coefficients

I have a list of expressions (they all are exact numeric quantities, not containing any variables), some of them have integer or rationals coefficients, or complex coefficients with rational or ...
2
votes
2answers
76 views

Trouble simplifying using Replace

I have the following expression: w.a.b.r+w.c.d.r I want to get: w.(a.b+c.d).r So far I used ReplaceRepeated: ...
3
votes
1answer
145 views

What role to sub/superscripts play in Mathematica?

I'm not sure I understand the role of subscripts and superscripts in the Mathematica language. For me, the expression: ...
1
vote
0answers
54 views

How to remove parts of an expression

I have an expression where terms Transpose[R].R appear. R is a matrix with the property Transpose[R].R=IdentityMatrix[3]. How ...
4
votes
3answers
316 views

How to get a list of monomials of a polynomial without coefficients?

Giving a polynomial, say a x^2 + b x y + c y^2 MonomialList[a x^2 + b x y + c y^2, {x, y}] just gives ...
4
votes
1answer
55 views

Boundedness of an expression

First post on this part of the stackexchange network, I was just wondering if Mathematica allows one to quickly see if an expression is always within a certain range given values for the parameters it ...
3
votes
2answers
79 views

Factor a specific sub-polynomial?

Consider the following example for a polynomial in several variables: ...
1
vote
0answers
64 views

Sequence of arbitrarily many variables separated by commas? [closed]

I am wondering if it is possible to produce an input such as x[1],x[2],x[3],...,x[n] for an arbitrary but fixed amount of n ...
2
votes
4answers
207 views

Is there a way to use array of data as a function variable?

I have a data that looks something like. {{1,1},{12,1},{7,9},{10,14}, ...... } I want to see if there is an easy way to apply this array of data into a ...
3
votes
3answers
142 views

How I can count multiplications in an experssion?

Next task to complete: Count *-symbol in such expression as a + s^2*b - c/y + o^3 + n*m*u (in this case count of ...
4
votes
1answer
86 views

What options need to be set for Simplify to perform a certain manipulations similar to FullSimplify?

Simplify performs algebraic transformations and is fast, while FullSimplify tries a wide range of transformations involving ...
0
votes
1answer
55 views

How can I manipulate a long expression to order it by factors/derivatives of a particular function?

I have a Mathematica notebook that generates a linear expression involving derivatives of a given variable. Expanded (and simplified for our purposes), it looks something like this: \begin{equation} ...
1
vote
1answer
52 views

2D plot using Manipulate command [closed]

Can anyone tell me what the problem is with the following code: y[x_ a_] := Sin[x (1 + a x)] Manipulate[Plot[y[x a], {x, 0, 6}], {a, 0, 2}] However, the ...
12
votes
1answer
172 views

Is there a way to control which special forms Normal converts?

Normal documentation reads: Normal[expr] converts expr to a normal expression, from a variety of special forms. But is there a way to control which special ...
1
vote
0answers
50 views

Analogue of Maple's `identify` command in Mathematica [duplicate]

In Maple there is a useful command identify that tries to find a closed form expression based on its numeric approximation. As far as I know there is no built-in ...
3
votes
2answers
84 views

Extracting subtree for a TreeForm

How can I extract an entire subtree from a TreeForm starting from a specific point of the tree? Because with Extract or Part you can take only that specific point...
6
votes
1answer
70 views

How to force evaluation of an expression with Part left unnevaluated?

My goal is to minimize a real valued multi-variable function averageFreeEnergyDensity. The function accepts an integer argument ...
0
votes
0answers
102 views

Loop in a loop, or how to evaluate complex expressions

I need to find $h_{0j}$ for every $1\leq j\leq300$, where \begin{multline*} h_{0j} = \sum_{q=1}^{Q}g_qe^{-\lambda_q j\Delta}\frac{e^{\lambda_q\Delta}-1}{\lambda_q} + \sum_{p=1}^{P}\frac{e^{-\alpha_p ...
2
votes
4answers
293 views

Print all numbers from a sequence which don't contain the digit 7

so i have this: Cases[RecurrenceTable[{a[n + 1] == 7 a[n] + n, a[1] == 1}, a, {n, 7}], Except[7]] But i noticed that it will only exclude numbers that are 7, and ...
0
votes
2answers
249 views

Get constant term with `Coefficient` for a non-polynomial

Take a nonlinear equation such as exp = (x + 3)/4 + Exp[x] + 1 + (c + x) Note that this is not a polynomial. Now, I want to extract the coefficients of this. ...
1
vote
1answer
97 views

Work around bugs in Summation, Hypergeometric function?

I'm so confused I don't even know how to phrase the question, so here's what's happening: I need an analytic form for this: ...
4
votes
1answer
94 views

Factoring out parts of an expression

I'm looking to factor out the parts of a multiplication type of expression. For example for the expression: $$20 e^{-t^2}\frac{t^2}{\sqrt{t^2+a}} erf(b+t)$$ I'd like to get a list in the form of: ...
1
vote
2answers
55 views

Subsituting expressions for expressions

I'm trying to define functions using other functions, like so: f[a_, b_] := a/b; a[c_] := c; b[d_] := d; Now what I want to be able to do is two things: ...
1
vote
3answers
207 views

How to manage list of list of rules?

Considering we have a list: str = "{1 -> {a -> aa, b -> bb}, 2 -> {2a -> \"{b -> bb}\"}}" Bringing this to expression gives: ...
2
votes
5answers
133 views

How to convert string to integer list?

Saying we have a string: "1 2 3 4 5 6" I want to convert this to integer list. First I do: ...
1
vote
2answers
86 views

How to list variables given equation? [closed]

Given an expression, is there any means to list variables? Example: a^3 + b^2 + c -> a,b,c I need this functionality because I am manipulating large expressions of many variables (20) and would ...
0
votes
0answers
30 views

Find out domain after change of variable in integral of d dimensions

Is there a way to tell Mathematica the change of variable you want to do and getting back the corresponding domain? The specific problem I am trying to solve is $\quad \quad\int_{-1}^0 ...
2
votes
1answer
187 views

How to parse string to expression? [closed]

When trying to make a string an expression I see some wrong results: ...
2
votes
2answers
137 views

Extracting numerical coefficients from an expression

I have very large expression and I want to extract and sum up all the numerical coefficients which multiply the summands. For example, expr = x + 2*y + 3*z*w ...
2
votes
1answer
92 views

Pull out scaling factor from a denominator

How do I force mathematica to just pull out the scaling factor of 1/r from this expression. (a+b)/r edit: Sorry, perhaps my earlier formulation of the question wasn't clear enough. I would like ...
0
votes
0answers
32 views

Extract the divergent/bounded part of a certain expression

Consider I have a power series which is function of $x$. A part of this expression is bounded when $x->\infty$, some remainder is on the other hand divergent when $x$ goes to infinity. What is the ...
1
vote
1answer
54 views

How to separate linear terms by output?

I am performing a complicated summation in which fa is a Sum of a[j] over j, and terms in fa end up containing a BesselJ, a Hypergeometric0F1, or neither. ...
5
votes
5answers
168 views

Isolating cross terms

I have a set of expressions that contains terms like $\frac{1}{(x + a + b)(c+d)}$. I would like to simplify the denominator so that products of $a,b,c,d$ are dropped, but $x c$ and $x d$ are kept. ...
1
vote
1answer
57 views

Expand an expression to only built in functions

This question is hard to phrase and even harder to google. Maybe it's best to explain it with a very simple example. ...
2
votes
3answers
106 views

Drop terms in expression

Suppose I have an expression of the this type: Quantity["Epsilonzero"] a (b + c Sin[ω t])^2 where t is time. I am interested in "extracting" the non ...