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.

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4
votes
3answers
56 views

Multiple output cells, suppressed by semicolon

I'd like to write a function that outputs multiple cells, as in Multiple output cells, but not when the function is called with a semicolon at the end. Any idea how?
0
votes
0answers
34 views

A function that takes in an array and returns an array (or lists)

So I have function f[x_] := c.x - Total[Log[b - A.x]] where the variables have dimension c is 1x100, b is 500x1, A is 500x100, and x is 100x1. My goal is to get the ...
3
votes
1answer
453 views

Gâteaux (directional) derivatives and higher order differentials of a functional

I would like to calculate the Gâteaux derivative of a functional (i.e. a function depending on functions). A simple example for the Dirichlet functional: $L(u(x))=\int_0^1 \frac{1}{2} (u'(x))^2 dx$ ...
6
votes
1answer
104 views

Filters on image vs data

I was using GaussianFilter and realized that applying it to an array yields a different result from applying it to an image. For instance: ...
0
votes
0answers
23 views
-2
votes
0answers
25 views

How to express the power series in term of function? [closed]

If S^n is differential operator defined as follows S^0 f(z) =f(z) S^1 f(z) =z f'(z) S^2 f(z) =z (S^1 f(z))' . . . S^n f(z)= z (s^{n-1}) Consider the function ...
40
votes
5answers
1k views

Why is there no PositionFunction in Mathematica?

Too often I have seen the programs of inexperienced users greatly slowed by using Position in an iterative fashion, when far faster would have been to compute a ...
3
votes
0answers
60 views

How to build a ColorFunction that can take a non-numeric value? Blend returns an error

I'm trying to use an external package, defined here. This package has a private function called makeColorFunction that essentially works by taking an input color ...
-5
votes
1answer
52 views

What is this function aimed to do?

Table[Sum[tmatrix[[i, j]], {i, 1, 2}], {j, 1, 2}] apparently creates some sort of a table, and it evidently works on a matrix....although it is hard for me to understand what should it do beyond ...
8
votes
1answer
186 views

How to efficiently write code with many functions that have variable number of iterators/arguments/

I am finding myself having to code functions like this: $$\text{answer} = \sum_{k_0 = 0}^{\color{Blue}n_0} \sum_{k_1=0}^{\color{Blue}n_1}\cdots\sum_{k_{N-1}=0}^{\color{Blue}n_{N-1}} ...
1
vote
1answer
55 views
10
votes
1answer
1k views

How does a Pringle lose its curvature?

Nom! As part of a bigger project, I've was writing some code to calculate the scalar curvature of surfaces of the form $z = f(x,y)$. This uses a general calculation of the scalar curvature to produce ...
1
vote
2answers
105 views

Function does not execute commands and fails to evaluate [closed]

The code I am trying to execute: hh[x_, y_] := x + y; hh[{3, 4}] The expected output: 7 However, on output I get ...
1
vote
1answer
76 views

Remove part within square brackets for function

So I've defined a variable as follows: q = {{x[t]}, {Φ[t]}} V=0.5*x[t]^2*m^2+0.5*Φ[t]^2*I I've had to differentiate with respect to time so: ...
8
votes
2answers
105 views

Why a function returns two different values if copied into a Notebook or imported with Get from a Wolfram Mathematica Package?

I have some Mathematica code that shows a behaviour I really cannot understand. The code only contains a bunch of function definitions. If I paste it in the Notebook Front End and I evaluate it, I ...
0
votes
0answers
49 views

What I make wrong with Module command;

I have a differential equations that I have to solve in two parts.e.g: ...
1
vote
1answer
52 views

Derivative in my package return 0

I'm writing my package (.m) in Mathematica and when I'll call the function returns 0 instead of right output. Here's my code: Package.m ...
1
vote
1answer
71 views

How to use recursion to find a logical dual

I want to make a little function that goes through a propositional formula and gives it's dual. Here is what I currently have: ...
0
votes
0answers
42 views

Greatest common denominator command. Can you explain why this command works?

Can you explain how this function works? mysteryFunction := Fold[#/#2 /. {n_~_~_ -> #/n, _ -> #2} &, #, {##}] &
7
votes
2answers
3k views

Module with “local functions”

I am trying to use a Module having "local functions", i.e., those which I need to define only inside this module. So I tried this: ...
3
votes
0answers
57 views

Custom units Compatible with Conversions [closed]

I am writing a Mathematica Palette to work with units, and am wondering if anyone knows a way to define new units outside of the standard ones that come with Mathematica 9. I do know of the ...
5
votes
2answers
272 views

Simpler way to type Derivative[1, 0][u][0, x]

Though not unbearable, I always feel a little nervous when typing partial derivatives at a specified place e.g. $u^{(1,0)}(0,x)$, which happens a lot when setting initial/boundary conditions for PDEs. ...
1
vote
2answers
124 views

How do I get Series[] as a functional, rather than as an expression (i.e. to avoid the dummy variable)?

How can I write an equivalent to Series that doesn't require a dummy variable? Note that the series should be constructed before the evaluation point is supplied, ...
0
votes
0answers
35 views

How to define a general linear function [duplicate]

I'm trying to work with a general linear function in Mathematica. I would like to assign some sort of rules to a function, say Tbar, to evaluate linearly. Basically what I would like to do is have ...
1
vote
0answers
36 views

Getting a list of function definition parameter values [closed]

If I define a function over certain values: f[0] = 1 f[1] = 2 f[2] = 3 How do I get the list of parameter values that it's been defined on? ...
2
votes
1answer
118 views

Syntax f[x_][y_]

Need to understand the principle of the distinction between f[x_,y_] and f[x_][y_] It seems also that z[x_, y_][a_, b_, c_][α_, β_] := a (x + y)^b + c/(α-β) ...
1
vote
0answers
62 views

Distinguish hashtag # operator when using multiple functions [duplicate]

I would like to do this list = Append[list[[#]],Map[list2[[1, #]] & , list[[#, 4]], {2}]] & /@ Range[Length[list]]; But I would like to substitute ...
1
vote
1answer
58 views
20
votes
1answer
457 views

How can I export my learned ClassiferFunction[] and PredictorFunction[]s?

Mathematica 10 provides beautiful high-level machine learning functionality. Sadly, the learned functions once created are rather opaque objects. I need to use them in other projects, so here is my ...
21
votes
7answers
1k views

Using patterns in pure functions

Pure functions may be handy if you don't want to assign your function a name. For example I would calculate $x(x-1)$ for some numbers $x$ by ...
9
votes
1answer
160 views

How to construct the RHS of Wick's theorem

I've been trying this for a few days now, but I just can't seem to find an efficient (speed-wise) functional way to code the following task. Context: I would like to construct an expressions that is ...
6
votes
1answer
33 views

How is Attributes protected and yet can still be set?

The Attributes function itself has the attributes: Attributes[Attributes] ...
9
votes
6answers
472 views

How to generate this structure of a list without `While` and the like?

I need to create a list that holds, for given integer d, the elements $1,\ldots,d,d+2,\ldots,2d,2d+3,\ldots,3d,3d+4,\ldots,d^2$ where $\ldots$ is just denoting ...
5
votes
3answers
164 views

Number by permutation

I want a function that compute number of permutation in lexicographical order. E.g. ...
2
votes
1answer
165 views

Passing function as argument

I've been mucking around with passing functions as arguments to other functions and via trial and error seem to have something that works. I was wondering if someone could have a quick look at some ...
1
vote
1answer
38 views

Plot is empty (probably) due to poor function definition

I am trying to plot my response $x(t)$ as a function of system parameter $M_0$. Here is my code to regenerate my problem ...
1
vote
2answers
95 views

n fold convolution of a function via a recursion function

I wanted to write a recursion function to calculate the n-th convolution of a function f[x_]. I wrote the function ...
7
votes
2answers
163 views

Sets and sums of different elements

Consider the set S={w,x,y,z}. If the set of all possible sums of any three different elements from S is {-1,3,5,8}, then what is the set S? How could I solve this function using Mathematica?
8
votes
2answers
97 views

For loop works at top-level but not in a function

Why does this work: For[i = 1, i <= Dimensions[list][[1]], i++, list = Insert[list, i, {i, 3}]] But this doesn't: ...
5
votes
1answer
75 views

How to obtain the Derivative of a pure Function of variable number of arguments?

Here is a function f that takes a variable number of arguments: f = Times[##]*Log[1 - Times[##]] & I now want to ...
0
votes
1answer
91 views

How to turn a subroutine into a function?

I've written a subroutine that takes in 6 matrices and after some manipulation returns back 3 new ones. I will use this subroutine fairly often in this notebook so I think it would be easier to turn ...
4
votes
2answers
99 views

How do I localize an assignment to expression (instead of symbol) within scoping construct?

Is it possible to localize an assignment to an expression (defined via UpSet) instead of a Symbol within a scoping construct? ...
0
votes
0answers
46 views

How to calculate a continuous function once and access values later?

I have a function that involves a numerical calculation: h[v_]:=NIntegrate[f[x]*Log[p[x, v]], {x, -Infinity, Infinity}] I need to visualize how well a bunch of ...
1
vote
1answer
52 views

AbsoluteTiming of nested integration gives strange result

I found somewhat strange behaviour of nested integration timings. Consider the following code: ...
1
vote
1answer
93 views

Plotting a periodic function [duplicate]

My question is the following: how can I plot a function repeatedly? By following some topics here I found some basic information about using Fourier series. This is what I made: ...
0
votes
1answer
38 views

Why doesn't this function definition work?

I am trying to define a following function (which is a convolution integral) ...
2
votes
2answers
113 views

How to set a values inside a custom function [duplicate]

I have a custom function like this stringLength[string_] := StringLength[ ToExpression[StringJoin[ToString /@ {del, string}]] = StringDelete[string, " "]] ...
1
vote
2answers
62 views

Finding roots of a function that includes Bessel functions [duplicate]

I'm fairly new to Mathematica so forgive any stupid mistakes. Here's my function: ...
0
votes
3answers
74 views

Write complex number in terms of absolute value and phase

I have a long vector and some of the values (19 out of 64) are complex. I got them using the Mathematica Rationalize function, so the complex ones are written in the a+bi form. Is there a function I ...