Questions tagged [expression-construction]

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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{...
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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
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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
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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 ...
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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{...
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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
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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
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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
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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 ...
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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
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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. ...
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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: ...
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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 ...
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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
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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
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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 ...
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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 ...
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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: ...
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0answers
58 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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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
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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
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1answer
81 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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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 ...
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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)) ?
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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
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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 ...
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0answers
78 views
4
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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
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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
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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
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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
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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: ...
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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
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3answers
179 views

How to make RawBoxes to be Expression

expr = First@ Level[Values@ WolframLanguageData["Plot", EntityProperty["WolframLanguageSymbol", "DocumentationExampleInputs"]], {3}] Plot[Sin[...
1
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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
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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
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1answer
77 views

Proper formulation of Do expression [closed]

I'm having trouble with the following code: ...
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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
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1answer
57 views

Get these edges whose degree is 2 [closed]

...
2
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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
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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
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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
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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 ...
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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
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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
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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
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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
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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
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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
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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?