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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1answer
423 views

Fitting parameters of user defined function returning discrete values

So, I'm fairly new to Mathematica (apologies in advance for the noobiness), and I'm having some problems regarding fitting the parameters of a user defined function to data. I'll give a representative ...
4
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2answers
78 views

How to sum values in the list that belongs to same week

I need to sum values that belongs to same week. For example, I have the list x with one column and n rows. Format: ...
1
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2answers
62 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? ...
2
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1answer
54 views
6
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1answer
185 views

Parentheses for negative integers

Trying to standard create prime factors presentation, but can't seem to remove the parentheses: ...
3
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1answer
43 views

Mapping also for one element (or telling it how to do so if head got changed)

Some code generates a polynomial, and has the form: expr = Plus[a[i],b[i],c[i],d[i]] I need to apply f to each term. To do ...
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0answers
27 views

How to make Expand work right in a function definition?

This works just fine: Derivative[n_, 1][g][x_, v_] := D[g[x, v], {x, n + 2}]/2 + D[D[g[x, v], x]^2/2, {x, n}]; h = Expand[D[g[x, v], {v, 3}]] I would like to ...
1
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1answer
82 views

How to form a variable from matrix elements

I have matrix with n rows and 2 columns, say m = {{x11, y12}, {x21, y22}, ..., {xn1, yn2}. Now, I want to form three new variables for example: ...
8
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3answers
123 views

Defining a custom Plus for a specific class of arguments

I'm trying to develop an domain-specific language with Mathematica. I want to define a customized behavior for the Plus function when applied to my data. For ...
1
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1answer
79 views

Plotting a function in {X(Y),Y} space

The code below generates some data and defines a function f[x,cb]:=NMaximize[expr,x] that upon being evaluated returns: {function value at max $x$,the function maximizing $x$}. ...
6
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3answers
187 views

How to get “Signature” of each element of “Permutation” output

I need to sum over all possible permutations, multiplied by the Signature of each permutation of a given list of symbols. But, I don't know how to determine the ...
1
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0answers
101 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
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2answers
71 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
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2answers
68 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
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2answers
62 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
579 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
51 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
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2answers
119 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 ...
7
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2answers
120 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
2k 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
194 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
votes
6answers
529 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
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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
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3answers
181 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
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3answers
96 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
89 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
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2answers
198 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. ...
2
votes
3answers
463 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
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2answers
111 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
36 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
250 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
97 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
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0answers
110 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: ...
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2answers
67 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
68 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
84 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
0answers
48 views

Fine tuning compiled code that computes dilogarithm function

As an exercise of writing a good Compile function, I want to do the simple task of coding a routine that outputs the real part of the dilogarithm function ...
2
votes
2answers
172 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
62 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
66 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
131 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
578 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
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2answers
49 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
90 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
271 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
158 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
72 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
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1answer
92 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 ...