Questions tagged [expression-manipulation]
How to manipulate expressions structurally, not necessarily complying with the rules of algebra.
617
questions
1
vote
0answers
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 ...
1
vote
0answers
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.
2
votes
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'...
0
votes
0answers
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 ...
1
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0answers
39 views
How to eliminate a variable from coupled ODEs?
I found this question with an answer:
How to eliminate variables in ODE?
...
3
votes
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.
...
1
vote
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:
...
7
votes
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 ...
2
votes
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:
...
5
votes
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 ...
0
votes
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: <...
2
votes
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)^-Ļµ
...
2
votes
1answer
57 views
How to extract terms from equation, and then set each of them to 0?
I have a long equation, namely,
...
6
votes
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 ...
1
vote
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 ...
2
votes
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} ...
2
votes
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:
...
0
votes
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:
...
1
vote
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
...
0
votes
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:
...
5
votes
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 ...
1
vote
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 ...
0
votes
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 $...
2
votes
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
...
2
votes
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 ...
4
votes
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-...
0
votes
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 $\omega\left(k\right)$:
...
1
vote
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:
<...
5
votes
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:
...
2
votes
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 ...
5
votes
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-...
5
votes
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^...
1
vote
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 ...
2
votes
1answer
58 views
Extracting coefficients from a sum of exponential functions
I'm dealing with a sum of exponential functions with different exponents
...
2
votes
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:
...
0
votes
0answers
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.
...
2
votes
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))}
...
2
votes
2answers
62 views
Symbolic nest expressions
I'm trying to understand how to use symbolic expressions as arguments. The following example represents my problem:
...
0
votes
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
votes
2answers
85 views
Collect with linear combinations
Is there a way to collect coefficients on specific linear combinations of variables? Consider the example below:
...
0
votes
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 Ī±, S1, T1, T2). I've tried replace, ...
2
votes
0answers
30 views
Computations with OptimizedExpressions without completely expanding them
I have to manipulate huge expressions that are rational functions of many (ā¼30) variables with integer coefficients. Storing them just as a ratio of two polynomials would be impractical. But they can ...
0
votes
0answers
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 ...
0
votes
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 ...
1
vote
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 ...
1
vote
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.
2
votes
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?
...
1
vote
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}+...
0
votes
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^...
2
votes
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 ...
