Questions tagged [expression-construction]

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Need to find a unique mathematical expression (not in documentation) that is as short as possible but takes a good amount of time to evaluate

I am writing a public ResourceFunction and I need a good clever use case that should not appear to emulate any examples in the official documentation but will ...
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1 vote
1 answer
105 views

How to convert this Mathematica expression to another, as described here?

I am working on a function of which the core will consist of something like: ...
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0 answers
56 views

Get depth of vertices in TreeGraph

I want to get the depth of each vertex in a TreeGraph, g. I might convert g into an ...
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  • 2,648
2 votes
0 answers
55 views

Store pattern names in variables, and use them in Condition (/;)

I am trying to create patterns whose form is not hard-coded, and which are not explicitly directly written. For that I want to use one list of pattern names to name some parts of a ...
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  • 483
0 votes
2 answers
30 views

How to turn FindFit result into function within a Module context

I'm trying to construct a 'normal' function (with formal parameter) from the FindFit result within a Module context. While this works on a global level: In := ...
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4 votes
1 answer
246 views

Why isn't this expression returning true to being positive when it is clearly positive?

Consider: ...
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4 votes
1 answer
120 views

Alternatives in pure function construction

When I declare a function f in the following form: f[a|b] := 1 then I can use it like: ...
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1 vote
2 answers
55 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 ...
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  • 1,004
2 votes
0 answers
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 ...
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  • 180
3 votes
2 answers
351 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 ...
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1 vote
4 answers
157 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{...
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1 vote
2 answers
109 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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  • 973
2 votes
1 answer
39 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 ...
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0 votes
1 answer
47 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 ...
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  • 153
3 votes
0 answers
138 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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2 votes
0 answers
60 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. ...
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  • 8,105
0 votes
1 answer
116 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: ...
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0 answers
46 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 ...
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1 vote
0 answers
97 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} ] ...
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  • 1,970
8 votes
2 answers
210 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 ...
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1 vote
3 answers
84 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 ...
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  • 181
0 votes
1 answer
60 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 ...
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  • 1,004
0 votes
1 answer
82 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: ...
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  • 3
0 votes
0 answers
64 views

Transform String to Expression [duplicate]

I have a variable postVector and another called CHKpostVector. Both are global variables. Only the variable ...
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  • 159
2 votes
3 answers
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?
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  • 1,649
3 votes
1 answer
82 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 $k$ ...
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3 votes
1 answer
89 views

Creat a matrix with boundary condition

I would creat a symmetric matrix, but how can I set the boundary in Subscript? ...
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  • 1,624
7 votes
2 answers
209 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 ...
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-5 votes
1 answer
77 views

Translation of GLSL expression (2) [closed]

What's the most compact WL translation of this GLSL expression: length(max(vec2(x,y),s)) ?
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0 answers
87 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: ...
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  • 2,703
21 votes
4 answers
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 ...
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  • 1,029
1 vote
0 answers
91 views

How to send Map[Plus[1, #] &, {1, 2, 3}] to Mathematica from C# via IKernelLink?

Here is a piece of my code ...
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  • 11
4 votes
4 answers
1k 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 ...
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4 votes
4 answers
380 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 ...
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  • 183
10 votes
3 answers
169 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} \...
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-1 votes
1 answer
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 ...
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  • 1
4 votes
3 answers
308 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: ...
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  • 3,896
1 vote
2 answers
89 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 ...
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  • 411
5 votes
3 answers
190 views

How to make RawBoxes to be Expression

expr = First@ Level[Values@ WolframLanguageData["Plot", EntityProperty["WolframLanguageSymbol", "DocumentationExampleInputs"]], {3}] Plot[Sin[...
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  • 23.4k
1 vote
4 answers
316 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 ...
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  • 411
4 votes
3 answers
310 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 ...
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  • 8,105
0 votes
1 answer
78 views

Proper formulation of Do expression [closed]

I'm having trouble with the following code: ...
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1 vote
0 answers
79 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 ...
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  • 711
0 votes
1 answer
58 views

Get these edges whose degree is 2 [closed]

...
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  • 23.4k
2 votes
1 answer
306 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 ...
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  • 711
0 votes
1 answer
88 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 ...
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6 votes
3 answers
528 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 ...
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  • 103
0 votes
1 answer
60 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 ...
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1 vote
2 answers
503 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 ...
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  • 1,726
3 votes
2 answers
1k 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, ...
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  • 1,726