Questions tagged [expression-construction]
The expression-construction tag has no usage guidance.
95
questions
0
votes
0answers
32 views
How to factor this expression
Consider the Jacobian:
$$ J = \begin{bmatrix}
-\frac{\beta I}{N} -\xi & -\frac{\beta S}{N} -\xi \\[1ex] \phantom{-}\frac{\beta I}{N} & \phantom{-}\frac{\beta S}{N} -\gamma \end{...
1
vote
2answers
49 views
Replacements: using condition to restrict to parts that satisfy a Boolean expression
I need to replace all integers k in a list with {k} and tried:
EDITED: as a clarification: I mean all integer elements of a list, not all integers in the list, so in the following example, only 4 ...
2
votes
0answers
32 views
Setting pieces of “matrices” - unwanted behavior
I am constructing matrices whose elements are lists themselves (of varying length), and am (re)setting the entries of these matrices using among others the "All" command. It seems that in ...
3
votes
2answers
194 views
Creating of the Jordan Canonical Form
I have a matrix polynomial P(s) and the Jordan blocks of P(s) corresponding to every eigenvalue sj (j=1,...,k).
How can the Jordan Canonical Form be generated, i.e. the block diagonal matrix which has ...
1
vote
4answers
114 views
Creating a block diagonal matrix when the submatrices in the diagonal are unknown
Let us assume that we have an integer $j$ $(j=1,2,...,k)$ and that for every $j$ is generated a matrix $P$ of dimensions $j$x$j$ . For example, if $j=1$ then $P=(-2)$.
If $j=2$ then
$$R = \begin{...
1
vote
2answers
76 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
1answer
38 views
Formula: setting parameters vs replacement, different results?
I have a question that may sound stupid and have an easy answer - but I currently do not see it.
I have defined a function of four variables, $f[a,b,c,d]=...$, in what I think is correct Mathematica ...
0
votes
1answer
44 views
Nest expressions of several arguments
I have the following function:
Q[r_, f_, s0_] := Q[r, f, s0] = F[r, s0] D[f[s0], s0]
By calling
Q[r, Q[r, f, s0], s0]
I ...
2
votes
0answers
39 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 ...
0
votes
0answers
39 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 ...
2
votes
0answers
54 views
How to do an arbitrary expression growth in Mathematica?
I want to write a function that can be used to grow an expression from a seed or another existing expression based on part specification.
...
0
votes
1answer
70 views
Help with printing table data
I am looking for the way of building a Table in a fast way. My true table evaluates huge functions with a system of differential equations . Let us for simplicity consider this:
...
0
votes
0answers
44 views
How to generate nested expression?
I've found some related questions, but nothing has really helped me to do what I want to do.
Given a list of variables L and a parameter ...
1
vote
0answers
91 views
Is there a good reason why `Slot[]` is not an atomic expression?
Here's a good reason why I think it should be,
Map[ If[AtomQ@#, #->"is an atom", #->"not an atom"]&
, {"hello",Range@3, # &}
, {-1}
]
...
8
votes
2answers
189 views
Using `With[…]` with a list specification as a variable [duplicate]
If you have some defined function, say f[a_, b_ c_, x], one can initialize this by using With[...] as
...
1
vote
3answers
83 views
Summation and product term expressed in Mathematica [duplicate]
I have the following term which I would like to express correctly in Mathematica:
$$\sum_{i=1}^{m}\frac{1}{\prod_{j=1,j\neq i}^m(\rho_i-\rho_j)}$$
This means that for $m=3$ for example you should ...
0
votes
1answer
44 views
Displaying positions in expression tree
Can one display the position of each character in an expression tree? For instance: g[h[i, h], l] should be displayed using TreeForm where each character is ...
0
votes
1answer
76 views
How to pass an expression as list elements for a Mathematica command
I'm trying to build a generic function that will calculate sums on different iterators.
To simplify let consider:
...
0
votes
0answers
58 views
Transform String to Expression [duplicate]
I have a variable postVector and another called CHKpostVector. Both are global variables.
Only the variable ...
2
votes
3answers
2k views
How to define constants in Mathematica like c1,c2,c3,…cn?
Manually defining the constants is tedious if the 'n' is large. how to do this?
3
votes
1answer
76 views
Generate multivariate monomials with constraints
I'm trying to generate multivariate monomials in variables $p_1, \ldots, p_n$. Each monomial has either $p_i$ as a factor, otherwise $(1-p_i)$. I need to generate all monomials which have exactly $k$ ...
3
votes
1answer
81 views
Creat a matrix with boundary condition
I would creat a symmetric matrix, but how can I set the boundary in Subscript?
...
7
votes
2answers
199 views
Constructing expressions using Sum vs Array[… Plus] vs Plus@@Table[…]
For constructing a sum of terms which are symbolic, I noticed that in addition to
...
-5
votes
1answer
73 views
Translation of GLSL expression (2) [closed]
What's the most compact WL translation of this GLSL expression:
length(max(vec2(x,y),s))
?
0
votes
0answers
73 views
Generate a system of linear differential equations from a coefficient matrix
I want to generate a system of linear equations that is stable. For that I generated random coefficients and divided the 10 by 10 matrix by the largest eigenvalue and set the diagonal to -1:
...
20
votes
4answers
1k views
Is expression in Mathematica well defined?
According to Mathematica, everything is an expression. So an atom is also an expression. But in other parts of documentation, they say that an expression is of form ...
1
vote
0answers
78 views
How to send Map[Plus[1, #] &, {1, 2, 3}] to Mathematica from C# via IKernelLink?
Here is a piece of my code
...
4
votes
4answers
891 views
Replace element of a matrix with condition
consider a matrix
$\left( \begin{array}{ccccc} 0 & 0 & 1 \\ 1 & 0 & 0 \\ 1 & 1 & 0
\\ \end{array}\right)$
How do I do a program that does these steps
1-Replace each ...
4
votes
4answers
321 views
Generating a family of 0-1 matrices satisfying a particular property
I'm looking for an elegant way to generate the set of all possible matrices that satisfy the following properties:
Each matrix has 9 rows and c columns, where 1<=c<=9.
Each matrix has exactly ...
10
votes
3answers
166 views
Graph that shows how symbols are used in an expression
I would like to make a graph to show how symbols build up an expression. For example, the matrix multiplication
$$
\left(
\begin{array}{ccc}
a & b & c \\
d & e & f \\
\end{array}
\...
-1
votes
1answer
50 views
Producing the same output as Tuples[{0, 1}, 4]? [closed]
How can I use the functions decimalToBinary and padWithZeros to produce the same output as ...
4
votes
3answers
297 views
Handling multi-part equations
How are multi-part equations best handled? For example, take the torsion equation:
We could express part of this equation like this:
...
1
vote
2answers
87 views
How to generate expression a + a1 e1 + a2 e2 + a12 e12 (subscripted)?
Sorry to ask this twice. I thought I could get away with just a0 + a1 e1 + a2 e2 + a3 e1 e2, but for my application I can't. I can generate a + a{1} e1 + a{2} e2 + a{12} e12 (subscripted), but that's ...
5
votes
3answers
179 views
How to make RawBoxes to be Expression
expr = First@
Level[Values@
WolframLanguageData["Plot",
EntityProperty["WolframLanguageSymbol",
"DocumentationExampleInputs"]], {3}]
Plot[Sin[...
1
vote
4answers
311 views
How can a generate an expression like a0 + a1 e1 + a2 e2 +a3 e3 + a4 e1 e2 + a5 e1 e3 + a6 e2 e3?
I wish to input n and then generate an expression. It would look like the above when $n = 3$. I would like to use subscripts for ...
4
votes
3answers
277 views
a function to extract all subexpressions from an expression
Can somebody help me with a function f such that it extract all sub expressions (i.e. looking down the expression tree) from any expression given to it and also a ...
0
votes
1answer
77 views
1
vote
0answers
71 views
How Defer[1+Evaluate[1+1] work?
I want to generate some expressions.
The expression is not evaluated expect some parts will evaluate first.
A simple example is
Defer[1+1+1] and in this expression ...
0
votes
1answer
57 views
2
votes
1answer
259 views
How to overload the operator “*” as KroneckerProduct [closed]
Can I use the expression below
a * b * c * d
for short to instead
KroneckerProduct[a,b,c,d]
automatically when a,b,c,d are ...
0
votes
1answer
83 views
Solving equations with change of variables is not working?
I want to express it in the form
$$\text{expr=}\int_{-\infty}^{\infty}C_1\exp\left(-t^2\right)f(t)dt$$, i.e., the integrand is a bounded smooth function $f(t)$ times $\exp(-t^2)$ and the domain of ...
6
votes
3answers
520 views
How to convert a string into a structured list
I am trying to use an efficient notation for the timing of sounds that i can play in Mathematica.
I would like to parse the string
"{ab{c{de}}f}"
as the list ...
0
votes
1answer
59 views
Is it the correct syntax with TransformedDistribution?
I define a function as f[x_] := ...;which is in fact the PDF of a random variable $X$. The PDF if given by $f_X(x)$.
Let $Y$ is a random variable, which is the ...
1
vote
2answers
472 views
How to find the lowest power in multi-variable expression?
I am sorry for asking a similar question again. I asked How to find the lowest power of variable in expression? and I got a wonderful answer, but I have one more question for a multi-variable ...
2
votes
2answers
877 views
How to find the lowest power of variable in expression?
If I have expression like
a1/x +a2/x^2 + a3/x^3
I want to return 1/x^3. In general case,
...
3
votes
2answers
98 views
Find most general 3-tensor under given constraint?
Consider A to be a general $2\times 2\times 2$ tensor:
A = Table[ a[i,j,k], {i, 1, 2}, {j, 1, 2}, {k, 1, 2}];
pictorially one ...
5
votes
1answer
273 views
How to represent 1 as Symbol[“Integer”]
Maybe this is a boring question, but I cannot figure it out. Because every expression has a Head, and Head[1] is ...
0
votes
1answer
794 views
Convert string to function with an argument
I am trying to build an expression by first writing it out as a string and then using ToExpression to convert it to an expression. However, I cannot figure out how to make expression recognize x as an ...
8
votes
5answers
1k views
Create a list of all possible multivariate monomials of a certain order
Given variables x[i] for i=1,2,...,n I would like to create a list of all possible multivariate monomials of order ...
0
votes
0answers
59 views
What is the meaning of #, Root and & [duplicate]
I am new, but can any one tell me what is the meaning of formulas of x and y in the picture?
