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.
170
questions with no upvoted or accepted answers
10
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0answers
173 views
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 ...
9
votes
0answers
206 views
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 ...
9
votes
0answers
113 views
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 ...
8
votes
0answers
158 views
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. [...]
...
4
votes
0answers
542 views
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
votes
0answers
317 views
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
...
3
votes
0answers
71 views
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
votes
0answers
64 views
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 $2 \times 2$ ...
3
votes
0answers
48 views
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] ?
...
3
votes
0answers
238 views
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 ...
3
votes
0answers
74 views
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
...
3
votes
0answers
155 views
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 ...
3
votes
0answers
378 views
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 ...
3
votes
0answers
117 views
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 \...
3
votes
0answers
323 views
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{...
3
votes
0answers
130 views
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 ...
2
votes
1answer
43 views
Why 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:
...
2
votes
0answers
34 views
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. ...
2
votes
0answers
54 views
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:
<...
2
votes
0answers
44 views
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 ...
2
votes
0answers
49 views
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 ...
2
votes
0answers
94 views
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, ...
2
votes
0answers
54 views
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 ...
2
votes
0answers
98 views
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 ...
2
votes
0answers
34 views
Keyed eigensystem for nested Association
Suppose a matrix is given where both rows and columns are keyed, for example this correlation matrix:
...
2
votes
0answers
33 views
Scoping of OptionValue for inner functions in closures
Assume a function f is a closure over an inner function g. Both f and ...
2
votes
0answers
100 views
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.
$...
2
votes
0answers
69 views
2
votes
0answers
75 views
2
votes
0answers
69 views
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)=?$$
for some $X$.
(I search, but I could ...
2
votes
0answers
71 views
Is there an efficient way to monitor the progress of a task remotely?
Recently, I've been running Mathematica packages on a remote cluster using SSH (using, e.g. the command
...
2
votes
0answers
123 views
Obtaining a Previously Constructed Function as Desired Output
I was playing around with some Generalized Trigonometric Functions defined as follows;
...
2
votes
0answers
70 views
First position of incremental series
I am still a beginner and maybe I want to do something too complicate!
After 29 cycles I obtained the following events list:
...
2
votes
0answers
56 views
Rescale large numerical factors in rational functions
Given a rational function
$$
f(x_1,x_2) = \dfrac{r_1 x_1^2 + r_2 x_2}{r_3 x_1 + r_4 x_2},
$$
with $r_i$ arbitrary real or complex numbers,
is there a built-in function to get Mathemtica to rewrite as
$...
2
votes
0answers
311 views
How to Implement a “Function Object” suitable for NDSolve and Finite Element Method?
I have a bunch of methods that shoud return an expression that behave like a function, i.e. an expression that, when supplied with suitable arguments, evaluate to something.
A simple ...
2
votes
0answers
152 views
Find algorithm or generator formula with automated procedure and pattern recognition
I am trying to find a generator formula for the discriminant of a polynomial and believe it would be an interesting problem for the Mathematica community to know how to automate evaluation of certain ...
2
votes
0answers
137 views
How to create a complex variable from dated list values
Can anyone help me to construct a variable "PI" from values of variable x.
Variable x represents a group of two time series rj and ri on equal dates(joined two dated lists with states).Variable x have ...
2
votes
0answers
457 views
Positive integrand giving negative answer
I'm integrating a positive function f(t) times sin(t) from 0 to pi/5 and get -38.
Actually f is slightly negative for a short time (smallest value ~ -0.0005), but far from enough to explain this. ...
2
votes
0answers
149 views
correct usage of ParallelTable
I am trying to parallelize my script. Here is a MWE of how I have done it:
...
2
votes
0answers
638 views
Generating a function which outputs possible chemical reactions
I want to make a list of chemical reactions and I write them down in a $\require{mhchem}\LaTeX$ format. They are of the following form
$$NA_n^i+MB_m^j \rightarrow \hat NA_{\hat n}^{\hat i}+\hat MA_{\...
1
vote
0answers
43 views
1
vote
0answers
77 views
Approximation of a function by a polynomial (Chebyshev First Kind, Bernstein, etc…) containing only even degrees and constants in a given Range[a,b]
In Mathematica, how can I create a polynomial function containing only even degrees and constants?
That is, I have a function:
$f(x)=\frac{\pi ^2}{\left(\frac{\pi }{2}-\tan ^{-1}(k (x-1))\right)^2}$
...
1
vote
0answers
45 views
Using `Block` with Conditions `/;`
I would like Block to run conditionally. I understand how to do one condition, but what about an AND operation?
e.g
...
1
vote
0answers
34 views
How to return a variable name and value from within a self-contained function block?
Abstract: I have viewed other solutions on StackExchange but none actually address using a fully self-contained function to return name and value of a variable. The only function that works requires ...
1
vote
0answers
27 views
How to avoid delayed evaluation in Condition used in a function definition
I would like to define a function (below, f) that evaluates only under the condition that some expression is True. The condition is to be specified now, and I don't want it to change for the purposes ...
1
vote
0answers
33 views
Unexpected output of a Listable function. Arguments not threaded correctly
I saw this question asking about the Listable. The accepted answer did a good explanation on the poor performance of user defined function with Listable. However the answer didn't clarify why the <...
1
vote
0answers
31 views
Is there a way to get the calling information inside the body of a function defined using down value?
Suppose a function has multiple argument structure like follows:
...
1
vote
0answers
42 views
1
vote
0answers
79 views
Issue with Solve, NSolve, FindRoot
I have this code that I've been trying to get working for some time. I asked some questions before which helped but still struggling!
...
1
vote
0answers
35 views
Plot is passing a bizarrely shifted x_min value to the user-specified Ticks function
The documentation for Mathematica's Ticks option says that you can specify the ticks for an axis by passing a function rather than a plain list description. The ...
