Questions tagged [expression-manipulation]

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

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22 views

Distinguishing function calls from multiplication when importing LaTeX via ToExpression and TeXForm

I'm trying to parse a LaTeX representation of a Desmos calculator (like this one) via Mathematica. Desmos exposes a JSON representation of its calculators, including a LaTeX representation of ...
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39 views

What is the difference between NSolve and N[Solve] [closed]

N[Solve] NSolve I am getting different results everytime I use these commands.
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2answers
68 views

How can I get output from Reduce assigned to a variable? [closed]

I use Reduce to solve an 3rd order equation, and the output is given as the OR'd combination the solution variable. Normally, I can do a replacement to assign the value to a variable, but that doesn'...
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50 views

Any way to automate solving problems where the answer from one question is used in the next?

I am a total Mathematica beginner. I just want to use it to do some calculations, and the reason it is so interesting and attractive to me as an engineering student is that it allows me to write maths ...
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39 views

How to eliminate a variable from coupled ODEs?

I found this question with an answer: How to eliminate variables in ODE? ...
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3answers
56 views

Computing the sum of the first row of a matrix

I wish to compute for the sum of the reciprocals of the first row of the distance matrix of a particular circulant graph. My code is as follows for the ordinary sum of the first row. ...
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1answer
92 views

Quantum bra and ket notations

Is there a way to define the above quantum expression in Mathematica. I am using an add on package in this link. http://homepage.cem.itesm.mx/lgomez/quantum/ What I have tried is: ...
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2answers
134 views

Better way to rename arguments to a functional form so that duplicate arguments are sequentially enumerated

I need to modify expressions that such as f[w, w, a, y, x, a, x, a] into f[w1, w2, a1, y, x1, a2, x2, a3]. In short, I have ...
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3answers
119 views

Simplifying expressions containing binary variables

Consider an expression with two binary variables, $a,b\in\left\{ 0,1\right\} $, given by $F=(1-a-b)^{3}(1-b)$, with truth table: ...
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4answers
189 views

Equivalent of select/remove for Mathematica?

What is the Mathematica equivalent of Maple's select/remove? To quote Maple: A typical application that uses select and remove ...
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0answers
28 views

Shorten a sum of many terms by introducing a rule for scalar product and Kronecker deltas and using repeated replacements

There is a sum of many terms that I would like to simplify by introducing a notation for scalar product of two vectors. Each term is a product of constants and of several components of 3D vectors: <...
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2answers
84 views

How to Simplify expression efficiently inside Power

How can I simplify trivial expressions under the Power? Here is one example: (z2p-z2p z3)^-ϵ ...
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1answer
57 views

How to extract terms from equation, and then set each of them to 0?

I have a long equation, namely, ...
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1answer
65 views

Collecting common powers of terms

How to collect the common powers appearing in the following function using MATHEMATICA, such that if I input (4 m^6)/((m - n)^2 (m + n)^4 (2m+n)^4) then the ...
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2answers
65 views

How to sort out/ extract positive and negative powers as list?

I have the following expression expr = x1^d1 * x2^d2 * x3^d3; where d1,d2,d3 can contain negative values/expression i.e. in ...
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3answers
117 views

Split matrix expression into multiple lines

Given a matrix expression testm = {a + b, c + d, e}; {# , testm[[ # ]] // Simplify} & /@ Range[ Length[testm] ] // MatrixForm \begin{equation}\begin{pmatrix} ...
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1answer
57 views

How to get the result in terms of a previously defined expression?

Say I have a vector X[n_] := Table[Subscript[x, i], {i, 1, n}] and a matrix of connections: ...
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0answers
28 views

Why are these expressions with shifted delta functions not equal?

I have the following equation Exp[a-t]*DiracDelta[t-a] == DiracDelta[t-a] which cannot be evaluated. However, if I plug in 0 for a: ...
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2answers
38 views

Substitute an expression iteratively

I have defined this function replaceIteratively[expr_, x_, list_] := Module[{n = 0}, expr /. x :> (n++; list[[n]])] which does the following job ...
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1answer
125 views

How can I obtain the matrices of coefficients of quadratic form?

I'm trying to find the matrices of coefficients of a quadratic form: ...
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1answer
122 views

How can I emulate Orderless attribute?

Suppose I want an expression to automatically sort its arguments. This can be done via SetAttributes[f, Orderless] f[3, 2, 1] (*output is f[1, 2, 3]*) Just as an ...
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0answers
41 views

Finding the domain in which a function is analytic with no imaginary part

I was wondering if it is easy to see if a given expression evaluates to a real number in a given domain? Let e.g. f(x,y,z) be some function depending on three ...
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1answer
80 views

How to check if an expression is real in some domain

I was wondering if it is easy to see if a given expression evaluates to a real number in a given domain? Let $f(x,y,z)$ be some function depending on three variables $x,y,z$. I would like to know if $...
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0answers
39 views

Define quaternions by properties instead of coordinates

I'd like to manipulate an expression of quaternions and only use the following properties ...
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1answer
84 views

Converting an equation to the form $ax+by=c$

I have a linear equation that comes as a result of applying orthogonality on a non-homogeneous boundary condition with two unknowns $C_1$ and $C_2$. Can someone help me to express this equation in the ...
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1answer
136 views

Simplifying the final coefficient expression of the solution to a Laplacian

I have been trying to solve a boundary value problem analytically which involves a three-dimensional temperature Laplacian over a parallelepiped. In the final step of my solution, using the two non-...
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0answers
35 views

Calculate density of states for 1D system

The density of states for a 1D system can be written as: $D\left(\omega\right)=\frac{L}{\pi}\frac{1}{d\omega\left(k\right)/dk}$ I have some expressions for $\omega\left(k\right)$: ...
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2answers
45 views

Substituting values from an association thread into a table of expressions

I have asked a question here. Yet I am trying to do the same procedure with AssociationThread Suppose I have the following function which is a normal distribution: <...
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1answer
47 views

Substituting elements of lists into an expression

Suppose I have the following lists, as = {1, 2, 3, 4}; bs = {10, 20, 30, 40}; and the following expression: ...
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1answer
49 views

Crown a list of two sublists with ErrorBar without losing list structure

I have a list with two sublists of numbers, e.g. Sigmaf = {{1,2,3},{3,4,5}}; ... and I would like to crown each number with ...
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1answer
72 views

Split Expression Into Constant And Non-Constant Summands

I have a partially t-dependent matrix which I want to split into its t-dependent and its t-...
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2answers
167 views

Replace a randomly chosen part of an expression

Given an arbitrary Mathematica expression, how can I choose a random part of the expression and replace it with another symbol of my choosing? For example, given $a x^3 +2y\cos(x)- \tanh(x^{y+3})/(x^...
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1answer
98 views

Fixed Point Iteration - Finding Iteration Functions

When we use Solve, it attempts to solve the system for the variables, for example Solve[x^3 + 4 x^2 - 10 == 0, x] If we want to use Fixed Point Iteration to ...
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1answer
58 views

Extracting coefficients from a sum of exponential functions

I'm dealing with a sum of exponential functions with different exponents ...
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1answer
32 views

Problem with recursive relations

Continuing the topic of my previous questions (link1 and link2), let me ask one more question. I have problems with the following code: ...
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55 views

check if one expression can be transformed into another

My question is how to use Mathematica to check if one expression can be transformed into another: Example 1: $ax^2+bx+c$ into $K\cdot(x+\alpha)^2+\beta$, and then show me $K(a,b,c)$ and so on. ...
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1answer
54 views

Replace a family of coefficients by a function in a sum

I would like to do something very simple, i.e. replace the coefficients in a sum by a function: c[1] + c[2] + c[3] /. {c[s] -> (s + 1)/(2 (2 s + 1))} ...
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2answers
62 views

Symbolic nest expressions

I'm trying to understand how to use symbolic expressions as arguments. The following example represents my problem: ...
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1answer
33 views

using pattern matching to separate coefficients and functions

I want to find out the coefficients and functions from an expression and possibly save them in separate files with same order. I have the following toy example: ...
2
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2answers
85 views

Collect with linear combinations

Is there a way to collect coefficients on specific linear combinations of variables? Consider the example below: ...
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0answers
32 views

Expanding complex expression and replacing variables in the result

When I'm finished expanding my expression I would like the result to be expressed again in terms of the original variables (like α, S1, T1, T2). I've tried replace, ...
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0answers
30 views

Computations with OptimizedExpressions without completely expanding them

I have to manipulate huge expressions that are rational functions of many (∼30) variables with integer coefficients. Storing them just as a ratio of two polynomials would be impractical. But they can ...
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38 views

Rearranging expressions by DragAndDrop

I see that the DragAndDrop option for editing is not supported anymore. However, I think this could be a really useful feature, for instance to rearrange the terms of an expression in the form we ...
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1answer
30 views

Applying function to both coefficients and variables in Collect

I am dealing with expressions schematically of the form expr = c[1] G[1] + c[3,8] G[3,8] + ... + c[3] G[1] + ... where the Gs are fixed objects, and the cs some ...
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0answers
53 views

Fast way to apply permutations in large list?

I have one Polynomial in the form of FF[x1,x2,x3,x4,x5,x6,x7,x8], where xi pick numbers from ...
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1answer
50 views

Optimizing an equation - show the length of an equation, including operators

A simple, but I think useful question to know the answer for. How can I quickly count the length in my equation, including +,-, and so on? For example, $x^2+1$ has a length of 4.
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3answers
79 views

How to hold the expression when using ToExpression with TeXForm

I know {1, 1} // Apply[Defer@*Plus] can return 1+1 But if I want hold the form from TeXForm,what should I do? ...
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0answers
30 views

Lexicographical Search and Conjugate

I bid you a good day. I want Mathematica to plug this assumed solution into the left hand side of a differential equation. Then collect terms of powers of $\alpha$. $\psi (x,y)=\alpha f_1(y)e^{i x}+...
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1answer
25 views

Testing expressions with === (SameQ) between original expression and after Factor[], Expand[] and FullSimplify[] [closed]

a=16x^4 y^5 (81-z^4)-54xy^2 (81-z^4) Out[30]= -54 xy^2 (81-z^4)+16 x^4 y^5 (81-z^4) b=Factor[a] Out[31]= 2 (27 xy^2-8 x^...
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1answer
62 views

How do I apply complicated algebraic/trigonometric manipulations to nested expressions?

Consider the expression $$ a\sin(x)-a\sin\left(\frac{x}{a}\left(a+\frac{ay}{x}\right)\right) \label{a}\tag{1} $$ which can be rewritten as $$ \sin(x)-\sin\left(x+y\right) \label{b} \tag{2} $$ and ...

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