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

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4
votes
1answer
59 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
98 views

Factor a specific sub-polynomial?

Consider the following example for a polynomial in several variables: ...
1
vote
0answers
75 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
208 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
146 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
93 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
64 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
176 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
97 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
81 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 n...
0
votes
0answers
121 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 j\...
2
votes
4answers
313 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
434 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
115 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
114 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
210 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
185 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
137 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 ...
2
votes
1answer
238 views

How to parse string to expression? [closed]

When trying to make a string an expression I see some wrong results: ...
2
votes
2answers
174 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
102 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
38 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
60 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
182 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
66 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
121 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 time-...
0
votes
3answers
57 views

Assigning a value to specific product [closed]

I was wondering if there is a way to assign a value to a specific problem. For example if I wanted $a\cdot a$ to equal $-1$. How would I go about doing that?
0
votes
1answer
139 views

Prevent a sum from simplifying? [duplicate]

Basically, I want to prevent a sum from cancelling or summing together the individual summands and just display them separately next to each other. Example: ...
0
votes
1answer
61 views

Why returning False? [closed]

Can anyone explain the false? I'm trying to grab co-efficient in front of X^2 I think. I say I think as I'm following my tutors example using his screenshot the only difference between his question ...
0
votes
1answer
54 views

Help for properly writing simple derivative expression

I need help to write the following expression (only 1 iteration): f(x) = ...some basic function... f[X0,...,Xp] = f(p)(x0) / p! What I have so far: ...
3
votes
4answers
296 views

Simplify binary expressions

Is it possible for Mathematica to do simplifications for expressions where the variables are binary, such as: a + b = 1 + 2*c => a + b = 1 Here c must be 0 because if it is 1, the RHS is 3 but ...
3
votes
1answer
143 views

Write Integer powers as products

I need to wirte all occasions of (a+b)^3,Ftp^2, Sin[th]^2, ...etc as (a+b)*(a+b)*(a+b), Ftp*Ftp, Sin[th]*Sin[th], ...etc ...
10
votes
2answers
360 views

Get rational and irrational parts

Consider an expression of the form $a + b \sqrt{2}$, where $a,b \in \mathbb{Q}$. How can I extract $b$ (or equivalently $a$) from this expression?
0
votes
1answer
53 views

Obtain the values of all Sub- and/or Superscripts from an expression?

Let Expr be an expression that can be practically any combination of variables. Now I can check whether this expression contains any subscripts or superscripts with ...
2
votes
3answers
559 views

Replace all integers by 1?

Let list1 be a list of variables of the form {c1 a, c2 b, ...} where $a,b,...\in\mathbb{C}$ and $c1,c2,...\in\mathbb{Z}$. I am ...
2
votes
1answer
60 views

How can I drop the “belongs to integers” part from Reduce output?

I have this Mathematica line: Reduce[1/(E^0)^x + 1/(E^1)^x + 1/(E^3)^x == 0, x] that gives the output: ...
2
votes
2answers
64 views

How do I extract the value of a 'Style'?

I have a Style displaying an underlying Real value. For example I might have ...
13
votes
2answers
353 views

How to do algebra on summations of variable expressions?

Is there any easy, general way to handle algebra on variable Sums? For examples, Gaussian Mixtures or Fourier Series: ...
2
votes
0answers
87 views

TrigExpand Idiosyncracies

TrigExpand[Sin[x]^2 Log[y]] returns sin^2(x) log(y), as one would expect. However, ...
1
vote
1answer
134 views

Collect powers of variables and integers separately?

Let expr contain a sum of powers of x with some coefficients ci. The exponents of ...
4
votes
1answer
310 views

Derivatives of functions with arbitrary number of variables?

I am trying to define a function f[x1,x2,...,xn] with n integer but not specified. And then I would like this funktion to behave ...
3
votes
1answer
49 views

Conditional replacement of all occurrences of a variable?

I know there is functionality in Mathematica to perform replacements like: x[a] d[a,b]/.y_[z_] d[z_,p_]->y[p] Which naturally gives ...
6
votes
4answers
182 views

Expression manipulation: Explode sums and products? [duplicate]

I wonder if the functionality exists to explode a sum, or product? What I mean by that is the following. Imagine, you have input data data = a + b c - d e f ; Is ...
2
votes
2answers
332 views

How can I get Solve to combine Sin/Cos into Tan?

I want to solve an equation in x, containing Sin[x], Cos[x] and a positive real constant <...
2
votes
1answer
81 views

Range and decimal digits [duplicate]

When I set Plot[Sin[x], {x, -2, -1}, Frame -> True, Axes -> False, FrameTicks -> {{Automatic, Automatic}, {Range[-2, -1, 0.2], Automatic}}] I ...
6
votes
6answers
271 views

Trying to write out the prime factorization of a number with CenterDot and Superscript

I am trying to use CenterDot and Superscript, in conjunction with Apply to write out the prime factorization of any given integer. Everything works well UNLESS the prime factorization of the number ...