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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5
votes
1answer
566 views

Nesting multiple functions of multiple variables

I was wondering how one would go about nesting multiple functions of, say, two variables. The problem comes from trying to implement the Chirikov standard map without using "for" cycles. I found a ...
22
votes
1answer
471 views

How to augment the realm of functions Mathematica thinks it knows how to integrate symbolically

My question involves extending the functionality of Integrate over specific integrals in the most generic manner. Specifically, is it possible to "hack into" ...
0
votes
2answers
185 views

Constraining two points, a specified distance apart, to a line

Suppose that I have two points in the xy plane: pt1 and pt2init. pt1 is fixed in space, ...
25
votes
4answers
519 views

How to make MapAt work with Span?

Span (;;) is very useful, but doesn't work with a lot of functions. Given the following input ...
6
votes
1answer
128 views

Property assignment on a graph vertex using PropertyValue does not work inside a function

I created this function: AddStone[board_Graph, v_, s : white | black | empty] := PropertyValue[{board, v}, VertexState] = s This function should change the ...
14
votes
3answers
233 views

What's wrong with this pattern of the form Except[Repeated[…]]?

I'm trying to build a head that recognizes molecules. Here's the code ...
13
votes
3answers
445 views

Is it possible to get the order of inputs when “overloading” an orderless function?

When working with symbolic matrix operations or other objects which don't have commutative multiplication, it would be nice to not have to constantly switch out times for ...
7
votes
1answer
616 views

How to find the smallest root

I have a continuous, differentiable, monotonic, bounded function called F[t]. If t -> Infinity then ...
6
votes
3answers
283 views

Using function with multiple definitions in Manipulate

I'm trying to use Manipulate to visually try out different values of lambda in a Box-Cox transformation. I've created a boxcox ...
4
votes
3answers
153 views

Constructing a function with Flat and OneIdentity attribute with the property that otimes[a]:>a

I want to have a function (called otimes) with the following two properties: it has the attribute OneIdentity and ...
13
votes
1answer
564 views

How to Combine Pattern Constraints and Default Values for Function Arguments

EDIT: As several respondents have noted in the answers and comments below, the original example had a default value that would never be used because of the way patterns and default values are ...
7
votes
3answers
186 views

Generating date ranges

How can I, in one line, generate all the dates with a constant day difference from one date to another? For example, if I'm interested in dates in the interval staring from 24.4.2012 till 2015 and a ...
11
votes
2answers
561 views

How to plot a barycentric line

I want to plot a barycentric function on an equilateral triangle (ternary plot). For example f1 = {Abs[Sin[x]], Mod[x, 2], Abs[Cos[x]]}; At the moment I evaluate ...
14
votes
5answers
736 views

Picking random items out of a list only once

I'm trying to create a function that randomly returns a value from a list but remembers the values that have been given before. At the end when the list is empty it should return an empty list. ...
7
votes
4answers
778 views

Force function to make assumptions about its input variables in Mathematica

I'm trying to force a Mathematica function to make an assumption about its input variables. In my case, I'm trying to define a function to return the pdf of a Gaussian. But let's use a simple toy ...
4
votes
1answer
216 views
4
votes
1answer
246 views

How do I use the result of Solve in a function definition?

I'm trying to adapt the following piece to the part where PowerF is a function of amax. ...
14
votes
2answers
339 views

Using several anonymous functions mixed together

This works: list // BarChart[#[[2]], ChartLabels -> DateString @@@ #[[1]], ChartStyle -> "Pastel"] & This doesn't: ...
4
votes
3answers
452 views

Integrating with multiple indicator functions

I am trying to calculate an integral involving multiple indicator functions, such as: $$ h(u,v,w) = -\int_0^1 J^{\prime\prime}(s) (I_{(0,s]}(u) - s)(I_{(0,s]}(v) - s)(I_{(0,s]}(w) - s)\, ...
4
votes
2answers
176 views

Calling a function an unspecified number of times

I would like to be able to call a function an unspecified number of times. That is, I would like the generalization of something like: ...
14
votes
6answers
769 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 ...
4
votes
1answer
190 views

What's the most intelligent way to store the information of a selfmade graph?

I have a very long list of element, say $a1,a2, a3$,..., and they are all connected in that each is the child of many parents. E.g. $a74$ is associated with $a2,a55,a71$, and also contains ...
7
votes
3answers
459 views

Composition of functions

I have a number of rotations computed by rot = RotationTransform[theta, point], and I would like to compose them to produce one function that is the composition of ...
9
votes
2answers
279 views

Defining a ForEach function

Consider the following function definition: ForEach[iterators__] := Table[#, iterators] &; Two questions about it: I. It works perfectly if you call it like ...
7
votes
3answers
483 views

Inverting a function in a certain region

InverseFunction works well for globally invertible functions, like f = 2*# + 2 &; InverseFunction[f] ...
14
votes
1answer
229 views

How to make a function like Set, but with a Block construct for the pattern names

How can we define a function that works like f[x_]=ComputeSomething[x] and treats x as a variable that does not have a value? ...
10
votes
3answers
681 views

Passing down arguments

In R, one can use ... to pass arguments down to another function. For example ...
11
votes
5answers
483 views

define a function from a list

I would like to create a mapping from a list and I am wondering if there is a slick way of doing it. For example, consider the list ...
36
votes
6answers
2k views

How can I create a function with optional arguments and options?

Is it possible to create a function with optional arguments that also takes options? Here is a simple example. I have a function f with option "g". It also has ...
41
votes
6answers
1k views

Functions vs. patterns

Every time I define a new function, I wonder which construct I should use: true functions obtained by using Function, or rule-based syntax. For example, these are ...
60
votes
4answers
2k views

Functions with Options

Suppose you want to create a function which has optional arguments. Maeder's book "Programming in Mathematica" covers the topic extensively up to version 3, but some things have changed/evolved since ...
15
votes
2answers
475 views

Constructing functions with variable number of output arguments

In Mathematica, you can construct a function f to have different definitions based on its input arguments. For example, ...
13
votes
2answers
345 views

SetAttributes[f,Flat]: Why the order dependence?

I'm experiencing a strange phenomenon. Here's a (quite artificial) test case: The following definition work just fine: ...
21
votes
3answers
1k views

Sum over n variables

What is the most painless way to sum over n variables, for example, if the range of summation is $i_1 < i_2 < i_3 < \dots < i_n$, where $n$ is an argument of the function in question? Is ...
24
votes
1answer
364 views

which is better, using Assert[] or manual checks on arguments and other computations?

I never used Asserts in Mathematica, but trying to see what advantage they have over just argument check and additional definitions of the function to capture unwanted input. For example, which one ...