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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0answers
108 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 ...
1
vote
2answers
99 views

What is the correct syntax for using a radio button to set values to be used elsewhere? (restated)

Here is my question, restated - I want to be able to choose the values for a complicated function from a set of alternatives values that I have gathered. The function requires several input values, ...
2
votes
2answers
99 views

Returning the 3-dimensional vector from a skew symmetric matrix

I'm trying to write a function that takes in a skew symmetric matrix and returns the corresponding vector. When I write the following code, it works when I leave it as variables, but it does not work ...
3
votes
2answers
63 views

Fast functional method for multiplying duplication numbers in a large list

Consider a list of symbols: mySet = {a, b, b, c, a, b, c, d}; I would like to form the product of duplication numbers. In the example above, I have 2 ...
14
votes
6answers
649 views

How can I evaluate only a single step of a recursive function?

Let's say have a simple recursive function for the Fibonacci sequence f[0] := 1 f[1] := 1 f[n_] := f[n - 1] + f[n - 2] but I want to see how it will expand in a ...
2
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1answer
58 views

Unprotect fails the first time, works on second pass [duplicate]

I am redefining some of the standard math functions. I know this is dangerous, so I am trying to be extra careful. (For instance, in the redefinitions, I make sure to only match a custom head) The ...
3
votes
2answers
160 views

How to define multiple functions using a for command

Let's say I want to plot 10 graphs of those following functions. Since they are recursive functions, I cant make a table with 10 different initial conditions because Mathematica stores each value ...
8
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2answers
136 views

using memoization with conditional statement

I would like some advice about the use of memoization in conjunction with conditional statements. Let me try to explain my problem: I am constructing a function depending on a number of parameters. ...
11
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7answers
3k views

Recursive function with if-statement

I am trying to represent the following function definition in Mathematica: $$\begin{align*} f(1)&=1 \\ f(2n)&= \begin{cases}f(n) & \text{if}\space n\equiv0\pmod{2} \\ 2f(n) & ...
2
votes
3answers
250 views

Extracting coefficients from a power series

I have a function defined explicitly as a power series: $$\sum_{n=0}^\infty{T_n}\frac{x^n}{n!}=\frac{\frac{x^3}{3!}}{e^x-1-x-\frac{x^2}{2!}}$$ and I would like to extract the coefficients $T_k$ as ...
26
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6answers
575 views

Constructing symbol definitions for With

I would like to be able to define two arrays, one containing symbol names and one containing the values of those symbols, for use in constructs such as With. For ...
29
votes
2answers
1k views

Best practice of passing a large number of parameters to functions

I have a number of functions that all take a large number of parameters. I am wondering what is the best practice of passing these parameters to those functions. I could, of course, simply specify ...
4
votes
3answers
191 views

How to re-parse (or re-map) character '.' to user-defined function

The default behavior of the character . between two non-numeric characters is to be interpreted as the infix of the Mathematica function ...
5
votes
3answers
120 views

Mapping a function of the form matrix[[row,column1;;column2]] over a list

I want to create a list of lists of values by mapping values[[row, col1;;col2]] over a list like {{r1,c1,c2},{r2,c2,c3},... } to ...
2
votes
1answer
117 views

defining Associated Stirling numbers of the Second Kind

First, I'm new to Mathematica. Spent my undergraduate programming with Maple and my computer crashed and I lost it. Fortunately, my university offers free Mathematica downloads to students, so here ...
6
votes
2answers
230 views

How to write complex function definitions at run time?

(Posting as a self-answered question to share a technique I discovered) In a certain project, I have many function definitions in which all parameters should be optional and come with default values. ...
4
votes
3answers
663 views

Constraining function found by NDSolve to stay positive

I am trying to constrain my variables in NDSolve so that they stay positive for the integration interval. Is is possible to do that? Using Assumptions as in ...
1
vote
2answers
116 views

function of derivative of a function

I know a similar question is answered somewhere, but it doesn't work for my case for some reason. I have the following problem in Mathematica. I want to compute f[h[x]]= x^2 + D[h[x],x]. Here, h[x] ...
0
votes
1answer
37 views

Rigging a function to output a distinct value every nth call

There's some fixed script I am unable to alter (keeping things simple: Table[f[i], {i, 1, 10}]), , however, I can alter a function that the script calls (again, ...
5
votes
2answers
274 views

Define a rule of derivative in NonCommutativeMultiply?

In tensor calculation, I need to do the following thing: Define a derivative operator Drv[fun,i], such that ...
2
votes
2answers
103 views

How to get `Series` to recognize user-defined function has pole

Edit for clarity: How does Mathematica's function Series know that Gamma[x] has a pole at ...
0
votes
0answers
119 views

How to create a reliable natural integral operator? [duplicate]

Natural integral is one of the antiderivatives of a function, for which the integration conctant is fixed in a natural way. It is defined as follows: ...
2
votes
0answers
124 views

Oddify an even function and vice versa?

I want to know how to construct a function in Mathematica which would produce even analog of odd function and vice versa in closed form? The mathematical definitions are as follows: ...
-1
votes
2answers
72 views

Plot not showing values

Still pretty new too Mathematica. Can someone please point out what im doing wrong when trying to plot the Dijkstra' s fusc function? code: ...
3
votes
1answer
82 views

Function of arguments given in non-fixed order [duplicate]

normally we define functions as f[x_, y_, z_] := ArcSin[x^2*y/z] however when one has many arguments (as I do) I find difficult to remember what is the meaning ...
2
votes
2answers
85 views

Creating function with matrix argument

I am completely new to programming, so I apologize in advance for a stupid question. I want to program an algorithm for computing invariant factors of a finitely generated abelian group, so in ...
2
votes
2answers
176 views

Constraining a random function

This question is a follow-up from here. I have a function that generates a list of correlations between some random variables: ...
2
votes
3answers
64 views

Reconstructing an expression [duplicate]

I have a nested expression like this one expr = Tan[Sin[Cos[x]]]; I can deconstruct it with ...
1
vote
1answer
70 views

Code check: Force simplified inequalities to be of form `expr > 0`

Simplify is a nice fast function that cleans up simple inequalities. For example: ...
5
votes
3answers
144 views

What is the recommended way to define numeric function with special cases?

What is the recommended way to define a purely numeric function with special cases? Should I define many special cases with pattern matching? ...
6
votes
5answers
839 views

Find function inverse

I'm trying to find the inverse of a function: (30*x^2 (1 - x)^2) (* where 0<x<1 *) I tried all the following options: 1. ...
1
vote
2answers
50 views

Indeterminate result from function, but not from equivalent expression [closed]

Can anyone explain this result? Why is one result Indeterminate and the other not? ...
3
votes
3answers
92 views

Defining a function that that evaluates a function to obtain a value not supplied as an optional argument

I have a function like this CentralDifferentMethod[α_, β_, α1_, α2_, λ_, v0_, dt_, t_] Now, I want to add a new parameter ...
2
votes
5answers
279 views

Returning all positions for all different occurences of elements in a list

Is there way to construct oneliner as pure function(s), so that I enter mylist only on one place - on the end of line. And that function return the same result as ...
6
votes
2answers
187 views

How to understand the process of ListCorrelate when it in two-dimensional condition?

Toady,I learn a function ListCorrelate,and I can understand process of execution his result in one-dimensional. However,the ...
2
votes
1answer
75 views

Using HoldFirst but not wishing to hold everything

I have a DynamicModule in which I go through some data analysis and keep or reject the results. Here is a toy example of what I am doing. ...
1
vote
1answer
93 views

Function returned an unexpected list

I was trying out a question in Wellin's Programming with Mathematica that says the following. Question: Given a set of points in the plane (or 3-space), find the maximum distance between any pair of ...
5
votes
0answers
203 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 ...
2
votes
0answers
73 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 ...
0
votes
1answer
56 views

Output a symbol from Module or Block

I have troubles to output an entire symbol, a function in this case, from a module or a block. For instance myf = Block[{f}, f[3] = 33; f[4] = 4; f] Then I want ...
8
votes
2answers
206 views

Error computing sum of sum of digits

I've defined a function that computes the sum of the base-b digits of n: DigitSum[n_, b_] := Total[IntegerDigits[n, b]] Then I defined a function that computes ...
1
vote
1answer
69 views
11
votes
4answers
276 views

Recognizing special cases of a defined function for permuted arguments

I have a number of ugly ways to implement the following pattern recognition task, but I'm looking for something elegant to keep my notebook tidy. I need to define a function of six variables ...
2
votes
2answers
111 views

How to make functions from datasets

I have a csv that encodes the results of plugging certain parameters (say, A and B) into certain functions (say, ...
1
vote
1answer
52 views

Specifying independence of a variable in a function

I am dealing with a function of a finite number of variables and among the operations I wish to do is to differentiate it repeatedly with respect with any of the variables. Now this function happens ...
2
votes
1answer
94 views

Defining a rule with functions of arbitrary arguments

I have a set of "functions operators", say A1[u],A2[u],A3[u],and I would like to define a rule such that, for instance, (x*A1[u1]).(y*A2[u2]) returns ...
1
vote
1answer
115 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 ...
2
votes
1answer
55 views

How do I tweak the input assistant to use string completion on my own functions? [duplicate]

I would like to be able to use Mathematica's string completion feature for subvalues of my own functions. I tend to go for functions that follow the pattern ...
2
votes
2answers
137 views

Local variables whose definitions depend on each other [duplicate]

Consider the following (pseudo-)function definition: f[l_] := Let[{ a = Length[l], b = First[l], c = b/a, }, c*10] So for ...