Questions on the basic structure of the Mathematica language (Wolfram language) including atomic data types, syntax etc
0
votes
0answers
47 views
How can I better formulate a conditional statement?
To solve optimization problems I have seen this:
Is there a more elegant way to do this with alternative conditional expressions? Is there something equivelant to ...
3
votes
1answer
44 views
Is it possible to write an expression A such that Evaluate[Evaluate[A]] is different from Evaluate[A]?
Mathematica is cool for all sorts of "magic tricks", but I'm trying to get an idea on how the core term-rewriting system works. Is it possible to make a term such that the output of its evaluation can ...
3
votes
2answers
101 views
The design implication of PD[X[ #, #, #, #], X[#, #, #, #]]
In Package KnotTheory, there's a function called PD[] that takes a tabulated knot and returns its PD codes, for example:
...
17
votes
1answer
242 views
Distinguishing Wolfram Language and Mathematica, the software
Which features are part of Mathematica, the software, and which features are Wolfram Language?
I would say there has to be a line discriminating the two somewhere. One could say that Mathematica, in ...
14
votes
3answers
192 views
What is the difference between Set and SetDelayed when evaluating the RHS leaves it unchanged?
I thought there was no difference between f[a_] = 2 + a; and f[a_] := 2 + a; because the resulting ...
3
votes
1answer
89 views
Why did Set work instead of SetDelayed?
I started with the following expression
a[t_] := -Pi Sin(Pi/2*t)
where initial velocity is 2 Pi and initial distance is 1.
...
4
votes
1answer
54 views
How can I evaluate only the (bound) variables in an expression?
Given an arbitrary expression, how can I have Mathematica only evaluate the (bound) symbols, i.e. replace them by their respective values, but not do any further simplification/evaluation of the ...
0
votes
1answer
34 views
FunctionExpand vs FullSimplify
The documentation (v.11.3) says: "FunctionExpand is automatically called by FullSimplify."
Why then does ...
1
vote
1answer
39 views
undesirable/buggy change in behavior of Limit in Mma 11.2?
The behavior of Limit changed in Mma 11.2, and I think it is in some ways undesirable or possibly buggy. Consider
...
1
vote
1answer
77 views
What resources can I use to become familiar with high level syntax?
I was reading a question about dropping higher order terms and realized that I have a serous gap in knowledge when it comes to the finer points of mathematica computational programming. Are there any ...
1
vote
0answers
42 views
What use is empty binding list in `Block[{},…]`? [duplicate]
Spelunking the Export function, I stumbled upon the following definition:
...
11
votes
1answer
107 views
stable sort for association?
Should I be able to use the "list of functions" approach to getting a stable sort of an association? In 11.1 I see,
...
7
votes
1answer
95 views
advantages of ApplySides?
Version 11.3 introduces ApplySides for situations where I usually use Map. What is an example where ...
3
votes
0answers
109 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 ...
10
votes
2answers
104 views
Can a Symbol have more than one OwnValue?
The DownValues, UpValues, and OwnValues functions are all plural. In general, a Symbol may ...
4
votes
1answer
69 views
SetDelayed not working as expected
According to the manual, "A variable defined with SetDelayed is evaluated every time it is used". The code below suggests otherwise.
...
12
votes
1answer
139 views
Check if symbol is in core language
How can I check if a symbol is pre-defined by Mathematica, in a way that's backwards compatible with old versions?
i.e. I would like some CoreLanguageQ[x_Symbol] ...
1
vote
0answers
32 views
Convenient value assignments in OOP
It is possible to implement OOP in Mathematica using something like
obj=c[<|a->1,b->2|>]
and it's convenient to extract value from the object by ...
0
votes
0answers
33 views
How can I extract the numerical value from the result of FindRoot [duplicate]
I've to use previous values of FindRoot to implement my program (recursively), but the type of the output from FindRoot is not a number. How can I extract the ...
4
votes
3answers
172 views
Keep only rules that replace integers with other integers
Let's say I have a list of replacement rules:
List1 = {2 -> 3, b -> 5.5, 6.57 -> 2, 3 -> 4.5, 1 -> -1, 0.03 -> 0.5, 9 -> a}
The desired ...
0
votes
2answers
47 views
Numerical integration with a fixed sampling size, skipping points [closed]
I have a large number of data points to integrate over numerically. I would like to sample only some of the points and use a rather large step size just to reduce computation time.
Say the data ...
0
votes
2answers
40 views
NIntegrating in $n$ dimensions?
I need to make a function that takes a function $f$ and a natural number $n$ and returns the integration from -inf to inf in all the $n$ dimensions of $f(x_1,\cdots,x_n)$. With Integrate I would do ...
1
vote
1answer
42 views
any possible meaning to a “terminal” slash (/)? [closed]
I've been directed to the web page
http://functions.wolfram.com/07.31.16.0001.01
The first statement in the formula is
...
-4
votes
1answer
71 views
how can i convert my matlab conde into mathematica or atleast convert the bisection program? [duplicate]
(Convert matlab code into mathematica code)
(I'm fairly new to mathematica)
(bisect function matlab code:)
...
0
votes
1answer
59 views
SplitBy and mod 2 [closed]
I wish to group semiprimes into groups with same parity. Mathematica does this well with
SplitBy[ Select[ Range@ 100, PrimeOmega@# == 2 &], Mod[#, 2] &]
...
0
votes
1answer
100 views
Why 1 is not recognized as real? [closed]
I'm not understanding smth simple. Why is 1 not recognized as a real number in the second line?
3
votes
2answers
153 views
Writing a bisection root finder
I'm trying to make a simple function that will calculate roots of equations by using bisection method. My code isn't working right. Can anyone take a look and help me?
Here is the code:
...
10
votes
1answer
330 views
What does the ToList function do, and where did it go?
I am trying to revive some code from 2015 (version 10?) which uses the function ToList. I can not find it defined in any notebook on my system (in fact, it only ...
-3
votes
3answers
186 views
11
votes
2answers
1k views
Can't understand one paragraph in Power Programming with Mathematica
In the chapter 7 of the Power Programming with Mathematica, there is a paragraph discussing the behavior of Set- functions: (page 205. (pdf version p. 224))
...
1
vote
0answers
34 views
Is Construct introduced to replace Function application? Should it be treated as such an alternative?
I noticed that v.11.3 got released the other day; it was exciting so I went through the Summary of New Features in 11.3 to catch a glimpse of what's new and see if there is something I should keep in ...
0
votes
1answer
91 views
Why is Null printing?
I am making a function that will evaluate several other functions, using the same inputs, in my program and give me the results. I am using Print to do this (see ...
2
votes
1answer
87 views
Can the pattern “_.” be used in head?
The standard usage of the pattern _. seems usually used in the parameter, for example, f_[a_,n_.]. I wonder if such pattern can ...
0
votes
0answers
33 views
Conditional access to entities in Wolfram knowledge base
I am trying to get the name of stars that are in a range of distances from the Sun. The Input I have tried is:
...
1
vote
2answers
35 views
How can I get a variable to be recognized as an array when computing expectation for multivariate distributions
The following expression works correctly:
Expectation[
x^4, {x, y, z} \[Distributed]
MultinormalDistribution[{0, 0, 0}, IdentityMatrix[3]]]
But when I ...
7
votes
1answer
54 views
Abort but keep what was already calculated
This is a very general question I have about aborting a running computation but keeping what was already generated.
Let's say that I perform a numerical optimization over a list of parameters. ...
1
vote
0answers
47 views
Is there a MaxPosition function? [duplicate]
The Max and Min functions return values, but I would like to have the position(s). Is there a standard function that does this? ...
1
vote
0answers
45 views
Why is Part designed to sometimes wrap the original head around the parts it extracts? [duplicate]
For me, the natural meaning of the function Part is "get the sub-expression at appointing position." It is quite unlike Take, <...
7
votes
3answers
282 views
Testing equality of graphics
Is there a way to reliably test the equality of two plots? Consider this:
plot1 = Plot[Sin[x], {x, 0, 2Pi}];
plot2 = Plot[Sin[x], {x, 0, 2Pi}];
You'd think ...
3
votes
3answers
122 views
aggregate records across dates
Each record in a dataset includes a country name, a year, and observations (e.g., GDP) for that country in that year. I would like to generate a new dataset with one record per country (so I would ...
10
votes
1answer
256 views
Why use pure functions?
I've now read the official documentation of wolfram on (anonymous) pure functions, and the part about (anonymous) pure functions in the book "mathematica programming intro".
I believe I understand ...
3
votes
2answers
93 views
What exactly do single brackets represent syntactically?
I'm trying to deepen my understanding of the mathematica language after having messed around with it for a long time.
I'm reading the book "mathematica programming Intro". Unfortunately, I don't ...
7
votes
0answers
93 views
Mathematica lexer: Numbers
This is a follow-up question to Mathematica lexer: Symbols and UTF-8 and this it is about numbers. In Mathematica, we have a large number of ways to input numbers. They can contain a notation for the ...
1
vote
2answers
29 views
Evaluating a 2D function successively with each pair of values in a list of pairs [closed]
I have a table of parameter pairs a and b {{a1, b1}, {a2, b2}, ...} and I would like to ...
1
vote
0answers
49 views
Is this expected behavior for With? Should it be replaced by Block? [duplicate]
Evaluating the following piece of code, returns-as expected-3:
g[a_] = a;
With[{a = 1},
2 + g[a]
]
Why does the following ...
1
vote
0answers
41 views
ClearAll works on all variables except “h”? [closed]
I have a seemingly very strange problem.
I have first defined a function $h$ as follows:
h[x_]:=x^2
And I also defined some other variables.
Then however, I ...
0
votes
0answers
41 views
Symbols in Mathematica (#, & etc) [duplicate]
I am constantly finding a lot of examples of usage of symbols
#
&
etc in the code. But I could not find any information what they actually mean and how to ...
11
votes
0answers
113 views
Mathematica lexer: Symbols and UTF-8
Did you ever wonder why here on our site, there is a highlighting difference between
f[argX_] := 1;
and
f[argα_] := 1;
...
5
votes
1answer
84 views
Is Depth[x, Heads->True] historical?
I randomly found that Depth has a boolean option called Heads:
...
1
vote
1answer
51 views
Functions defined with numbers
If I have defined functions as "A1", "A2" ecc. then I have many function as A+number, can I define a For cycle to call these functions (they have all the same kind of arguments) once?
Something like
...
