Questions tagged [expression-construction]

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5
votes
3answers
564 views

Getting a usable expression tree

I need to get the expression tree for some expression. expr //TreeForm The above grabs the expression tree but it isn't in some sort of usable format. Just an ...
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} ] ...
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 ...
17
votes
2answers
603 views

Additive SparseArray Assembly

The goal is to assemble a SparseArray in an additive fashion. Let us assume we have a large List of indices (some will be ...
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
212 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
115 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
77 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 ...
3
votes
1answer
336 views

Arrange equation in normal form

Is there a way, or if not, how could one define a function which takes an equation in any form (for example as given by FullSimplify): $$(A+X_0) x+By=3x$$ and ...
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 ...
47
votes
3answers
16k views

How to form a block-diagonal matrix from a list of matrices?

For example, like this: I know Join works, but it is a bit troublesome for multiple matrices. I also tried DiagonalMatrix, but ...
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 ...
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
75 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 ...
8
votes
2answers
190 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
45 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
61 views

Transform String to Expression [duplicate]

I have a variable postVector and another called CHKpostVector. Both are global variables. Only the variable ...
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} \...
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
83 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
201 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 ...
10
votes
4answers
1k views

An inverted pyramid

I want to draw a pyramid approximately like this ...
1
vote
2answers
475 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 ...
-5
votes
1answer
74 views

Translation of GLSL expression (2) [closed]

What's the most compact WL translation of this GLSL expression: length(max(vec2(x,y),s)) ?
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 ...
0
votes
0answers
76 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: ...
4
votes
4answers
915 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 ...
7
votes
3answers
1k views

How to create a large sparse block matrix

I need to generate a very large sparse block matrix, with blocks consisting only of ones along the diagonal. I have tried several ways of doing this, but I seem to always run out of memory. The ...
4
votes
4answers
328 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 ...
-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
299 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: ...
4
votes
1answer
238 views

Adapting old Arrow expressions

I have an old notebook that uses the now obsolete Arrow package. For example, I have an expression containing ...
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 ...
1
vote
4answers
314 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 ...
5
votes
3answers
180 views

How to make RawBoxes to be Expression

expr = First@ Level[Values@ WolframLanguageData["Plot", EntityProperty["WolframLanguageSymbol", "DocumentationExampleInputs"]], {3}] Plot[Sin[...
7
votes
5answers
638 views

Elegant method of generating this matrix?

Good evening, I need to determine an elegant (as possible) method of computing an $n\times n$ matrix below (the matrix shown is just a $16\times16$ example). I've been toying with ...
4
votes
3answers
279 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
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 ...
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 ...
0
votes
1answer
77 views

Proper formulation of Do expression [closed]

I'm having trouble with the following code: ...
1
vote
0answers
72 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 ...
2
votes
1answer
262 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
57 views
6
votes
3answers
521 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 ...