Questions tagged [function-construction]
For questions on writing functions (pure or using Set/SetDelayed) for any purpose, including the features that may be incorporated in those functions, such as options, patterns and conditions.
227
questions with no upvoted or accepted answers
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What is the best and most efficient way to curry?
Suppose I have a function with a signature like g[expr, _?(f), {1}, Heads -> False] and I want to access it as an operator by giving the first argument last. I ...
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Does Compilation option "InlineExternalDefinitions"/"InlineCompiledFunctions" lead to unnecessarily complicated nesting?
Question: When an external (possibly complicated) definition f is used inside a compiled function with ...
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Does ArgumentsOptions do anything we couldn't do without it?
ArgumentsOptions was new in version 12.2. I looked at the application on that page, and it makes code very difficult to understand. What if anything does ArgumentsOptions do for us that we couldn't do ...
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Fast Destructuring
This might be a XY problem. I first post my immediate question and some background below.
Question: What's the fastest way to pass arguments matching ...
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Defining a SparseArray functions in Mathematica 13
I am defining a sparse array as a function of argument x, i.e.
f[x_] = SparseArray[{1->x}, {3}]
In Mathematica 12 this works perfectly, I can pass arguments and ...
- 81
8
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163
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KeyValuePattern specificity in DownValues
Bug introduced in 10.4.0 and persisting through 11.3.0
CASE:3824590
[...] Developers are discussing this behavior. [...] I will let you know when I have definite information on this. [...]
...
Kuba♦
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69
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Why does Longest not work on OptionsPattern?
When having a function with optional arguments and options, I frequently find myself writing something like this:
...
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6
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254
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Finding periodic cycles of a function
Given a function f[{x,y}] it is rather simple to use, for example, NSolve to find periodic points of period $n$. We simply take ...
- 713
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35
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Efficiently threading with a default value for missing parts / defining custom behavior for addition of expressions with a given head
In short, I would like to be able to "add" expressions with a particular head (call it h for our purposes) which will always appear with a sequence of (...
- 61
4
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answer
473
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Return unevaluated expression from function
Is there any way (except using upvalues) to make a function that returns it's input Unevaluated? What I mean by that:
Take the following example:
...
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4
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975
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Wick Contractions; help with a piece of code
An alternative title to this thread could be, understanding another person's code.
A few years back there was a workshop on Mathematica and applications to theoretical physics; if you want I can ...
- 4,206
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339
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Strange behaviour of MMA in derivatives of some standard functions
There are some peculiar things to be discovered in derivatives of some standard functions in MMA:
Strange behaviour
Example 1: Abs
We have
...
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52
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How can one automatically arrange the connections of a circuit with as few crossings as possible, given a set of edges?
Here are two functions to create symbols of dc voltage source and a resistor.
...
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76
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What are some ways to overload Min in order for it to work with user defined expressions?
I have defined size to work with discrete size labels:
...
3
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116
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Prime Matrix with determinant of powers $2^x$
Mathematica has commands for finding prime matrices, for example, here is a matrix with randoms in the range $<100$:
RandomPrime[100, {3, 3}]
This $2 \times 2$ ...
- 2,702
3
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60
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Differences between u[x,y,t] vs. u[x,y][t] vs. u[x][y][t]
Is there any difference between defining a variable by u[x,y,t] or u[x,y][t] or u[x][y][t] ?
...
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158
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Fast way to check if an expression matches any of the rules in a list?
I have a function defined roughly like so. This is a minimum recreation.
foo[expr_, rules: {__Rule}] := "some fancy result" /; AnyRuleMatchesQ[expr, rules];
What ...
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383
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How to achieve with Mathematica the effect a closure has in other languages?
Motivation
I want to write an auxiliary function (brief auxf) for testing the output of another function that evaluates its body repeatedly using ...
- 4,115
3
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78
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What's the role of the lines order in defining a function?
I'm totally surprised by the finding I had never noticed before.
This code works as obviously intended
...
- 1,843
3
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168
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How to reduce computation time for a large symbolic matrix
I have a 6x6 matrix (A) that is a function of k and H with complex symbolic entries that contain functions. I want to reduce the computational time since I will be evaluating the matrix many times for ...
- 31
3
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442
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Generating a list of random numbers that follows a pattern
I'm a beginner to Mathematica. I'm writing a code to design a 4-bar linkage mechanism that traces a path in 2D space. I got the modelling done right, now I'm writing my own implementation of a genetic ...
- 307
3
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125
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How to get this terrible summation/product to run in Mathematica?
I've come across this formula and have no idea where to even start. (My assumption here is that $m,n$ are known and input into the expression to arrive at an answer.)
$$f(m,n) = \sum_{\substack{0 \...
- 143
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627
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Lyapunov Exponent as a function of parameter
I am working at Rossler system and I would like to ask you for some help.
This system is described by equations:
\begin{array}{ll}
\dot{x} = -y - z \\
\dot{y} = x + 0.2y \\ \label{eq:UkladRosSP}
\dot{...
- 59
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143
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How to make a new analytic function work seamlessly with Mathematica's analysis functions?
I am defining a new analytic function of six variables. I have algorithms to evaluate it numerically, and have amassed a large catalog of analytic properties.
It is easy for me to program the ...
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2
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89
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How to write 2D finite volume solver in a functional approach?
I'm solving 2D poisson problem of a finite volume problem using TDMA.
The solution of the problem is given:
\[Phi][x_, y_] := x^2 y + x y^2 + 1
The definitions are ...
- 41
2
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answers
66
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Argument value loss using Listable C-Compiled Function
In my recent studies, I have come across a very strange anomaly with C compiled functions. When I call a function that has the 'Listable' attribute while global variables are accessed through ...
2
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answers
54
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How to separate coefficient and argument of the function?
I'm trying to make a list with coefficient and argument of the function f as below.
myList is my input and ...
- 2,832
2
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answers
96
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How does Mathematica choose which function definition to use?
I was wondering what the process of matching function arguments arguments against different function definitions actually looks like for Mathematica.
(Just to be clear, I'm not simply looking for an ...
- 8,825
2
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answers
40
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Rules of operation
I am trying to implement the following. But the first four lines are not implementing in my rules!!!
...
- 1,225
2
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answers
1k
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General:: Exp[-717.401] is too small to represent as a normalized machine number; precision may be lost
I am solving pde.
For the post processing bvp, there is solution given in output which is the solution from mathematica version 10.0.1.
Output from above in mathematica 10.0.1 is,
But when the similar ...
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1
answer
155
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Why do some variables get substituted and others don't?
I was running into some trouble with my math and I whittled it down to this nugget:
...
- 31
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265
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How to define tensors similar to Riemann tensor in xAct xTensor xTras
I'm working on a project where we deal with objects very similar to Riemann tensor. In fact they are Christoffel symbols for higher spins. I'm using xTras for modeling problems in wolfram mathematica. ...
- 145
2
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115
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How to override a built-in Mathematica function using its old version?
How can we override a Mathematica built-in function using itself in the definition?
For example, the DiracDelta function is not defined for complex numbers like:
<...
- 1,536
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118
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How to handle Units when Integrating?
I have some functions defined, which are to use units. Now another function is used to integrate over those, with the integration variable also quantified and the input to said function. I better just ...
- 83
2
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answers
125
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Speeding up the process of NDSolve[] when a user-defined function is involved?
I am trying to tackle a (1+4 dimensional PDE) model at which the solution of the first PDE (with some interpolations and changing the domain) would be used in the second PDE.
In fact, I must choose ...
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2
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190
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Lambda calculus reduction in Mathematica
Are there any built-in functions for reducing lambda terms in Mathematica? If not, how might one do it? I've heard of Function, which is good for $\beta$-reduction, ...
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157
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2
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115
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Why does the evaluation of "Catch[Break[],\$Failed]" not return "\$Failed"?
Under normal conditions, evaluating something that emits a Message eg the evaluation of
1/0
that produces a ...
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2
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40
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Keyed eigensystem for nested Association
Suppose a matrix is given where both rows and columns are keyed, for example this correlation matrix:
...
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2
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answers
51
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Scoping of OptionValue for inner functions in closures
Assume a function f is a closure over an inner function g. Both f and ...
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2
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183
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Defining a function by coordinates of points and degree of a polynomial
I'm studying about solid of revolution.
In these studies, I learned that to get the volume of such a solid, I need to know $f(x)$ to describe the contour of the profile. This concept I understood.
$...
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75
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2
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0
answers
88
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2
votes
0
answers
95
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Built-in functions for Homotopy group
Does Mathematica have built-in functions for Homotopy group, for example for computing
$$\pi_n(S^m)=?$$
or more generally
$n$-th homotopy group,
$$\pi_n(X)=?$$
for some $X$.
(I search, but I could ...
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answers
86
views
Is there an efficient way to monitor the progress of a task remotely?
Recently, I've been running Mathematica packages on a remote cluster using SSH (using, e.g. the command
...
- 51
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votes
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answers
131
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Obtaining a Previously Constructed Function as Desired Output
I was playing around with some Generalized Trigonometric Functions defined as follows;
...
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74
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First position of incremental series
I am still a beginner and maybe I want to do something too complicate!
After 29 cycles I obtained the following events list:
...
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67
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Rescale large numerical factors in rational functions
Given a rational function
$$
f(x_1,x_2) = \dfrac{r_1 x_1^2 + r_2 x_2}{r_3 x_1 + r_4 x_2},
$$
with $r_i$ arbitrary real or complex numbers,
is there a built-in function to get Mathemtica to rewrite as
$...
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584
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Defining a function with a subscripted head
How can I define a function with subscript?
Forexample:
f_alpha[x] = 2*x
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How to Implement a "Function Object" suitable for NDSolve and Finite Element Method?
I have a bunch of methods that shoud return an expression that behave like a function, i.e. an expression that, when supplied with suitable arguments, evaluate to something.
A simple ...
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