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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1
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1answer
57 views

How may I repeat this procedure n times?

This is the procedure ...
1
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2answers
125 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 ...
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 ...
8
votes
2answers
111 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
52 views

What I make wrong with Module command;

I have a differential equations that I have to solve in two parts.e.g: ...
1
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1answer
56 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 ...
0
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0answers
43 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} &, #, {##}] &
5
votes
2answers
280 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. ...
3
votes
0answers
60 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 ...
1
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1answer
73 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
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0answers
36 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
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0answers
39 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? ...
1
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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 ...
2
votes
1answer
127 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
1answer
63 views

User-defined density plotting function with a functional argument: extracting variables from the function and plotting in a circular region

I would like to customize the function DensityPlot and use it in a package as a function called MyDensityPlot: The functions ...
6
votes
1answer
38 views

How is Attributes protected and yet can still be set?

The Attributes function itself has the attributes: Attributes[Attributes] ...
10
votes
1answer
195 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 ...
5
votes
3answers
180 views

Number by permutation

I want a function that compute number of permutation in lexicographical order. E.g. ...
9
votes
6answers
477 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 ...
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 ...
8
votes
2answers
98 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: ...
7
votes
2answers
169 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?
1
vote
1answer
79 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: ...
5
votes
1answer
78 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
0answers
49 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: ...
3
votes
1answer
54 views

Equivalent (?) definitions of function gives different answers

I have a function as follows: ...
0
votes
1answer
42 views

Why doesn't this function definition work?

I am trying to define a following function (which is a convolution integral) ...
1
vote
1answer
100 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: ...
1
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2answers
79 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
89 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 ...
0
votes
1answer
92 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 ...
1
vote
2answers
107 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 ...
0
votes
0answers
59 views

Considering special cases in general definitions

I want to calculate some coefficients $\qquad B_k = 2\int_0^1 u(x) \cos(k\pi x)\,dx$ for $0<k\in\mathbb N$ and I am doing this in the following way: ...
0
votes
0answers
56 views

break down the function

I am using Series function, but I found that it cost too much time. Since the Series function is Taylor expansion and I only need first order, I want to break down the code, so I can make it faster <...
2
votes
1answer
49 views

Passing a list to a nested vector function

In order to apply a newton-rhapson algorithm to solve a set of nonlinear vector equations such as these, f[x_, y_] = {x^2 - 3*y + 6, (y + 1)^2 - x - 33} I need ...
1
vote
2answers
89 views

Partial Function Evaluation [closed]

How can I evaluate only part of a stack of function calls? In particular, given f[x_,y_,z_]=x+y+z;, say, I'd like to define a function ...
19
votes
3answers
394 views

Writing functions with “Method” options

I'd like to implement several behaviors for a particular function using a Method option added to the function definition: ...
5
votes
4answers
96 views

Multi-index variable depending on signature of permutation of indices

I do have some multi-indexed variable, e.g. like this \begin{align*}f_{123} &= 1\\f_{345} &= 1/2\end{align*} where $f$ is antisymmetric under permutation of any pair of indices, i.e. e.g. $...
1
vote
1answer
41 views

How to use Composition when the functions have two parameter

There are some basic instructions about Composition on this site, but I'm still confused on how to use it when the functions I am composing have two parameter, such ...
2
votes
2answers
116 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, " "]] ...
4
votes
1answer
68 views

How to use currying to write a tail recursive function for summing factorials given a certain bound

I am very confused about how can i use currying to write a tail recursive function for summing factorials within a certain bound or summing the bounds i.e. given [1,5] i should be getting 1!+2!+3!+4!+...
3
votes
2answers
256 views

Why can't FindFit get the proper result in this problem?

Cross-posted in http://tieba.baidu.com/p/4425634583 The mathematica helps me solve one differential equation in numerial method and got the data of the answer,but the taylor series fit is not good in ...
3
votes
1answer
71 views

Mod[k, 2] == 0 versus EvenQ[k] [duplicate]

I'm having some trouble with Mod[k, 2] == 0 versus EvenQ[k] They are sometimes yielding different results when given the ...
0
votes
1answer
47 views

ND on a function using NIntegrate

I need to numerically differentiate a function that takes a list as an argument and that uses NIntegrate in its definition. A simple example is ...
4
votes
1answer
91 views

Writing a function that finds the difference between two maxima

Suppose i have two functions: $\qquad -2x^2 +5x+3$ and $\qquad -5x^2 +2x+3$ To solve the point where the functions are at maximum i use the command NMaximize ...
4
votes
1answer
127 views

Jackson Integral

Following an old post, I have tried to make a function that calculates the Jackson integral of $q$-calculus: ...
0
votes
0answers
60 views

Normal ordering in Mathematica

I want to create a function which normally orders a string of field operators. Consider the following: $$\langle0\vert\hat{a}(k_n) \cdots \hat{a}(k_2)\hat{a}(k_1)\hat{a}^\dagger(k_1)\hat{a}^\dagger(...
0
votes
1answer
42 views

Finding text files in a given path and applying a function to those files

I made a function called "SolveLinearSystem[]" that solves,as its name suggests, a linear system of any amount of variables. It takes the path of a text file as its only argument. The function then ...