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.

learn more… | top users | synonyms

0
votes
1answer
129 views

Strange function definition result [duplicate]

I'm relatively new to Mathematica, and I'm trying to define a function f(k) that would do the following: For any positive integer $k$, a finite sequence $a_i$ of fractions $\frac{x_i}{y_i}$ is ...
2
votes
2answers
393 views
35
votes
4answers
891 views

Enforcing correct variable bindings and avoiding renamings for conflicting variables in nested scoping constructs

Using global variables the following turns an "expression" into a Function: expr = 2 x; Function[x, Evaluate[expr]] Of course ...
5
votes
1answer
238 views

How to find the name of the current function

I would like to know the name of the current function from within that function. For example, consider the following code ...
1
vote
1answer
273 views

Function definition and delayed assignment

I need to define the following function MyWavelet[n_]["PrimalLowpass", prec_ : MachinePrecision] := Table[(-1)^(j - 1) h[[2*n - j]], {j, 0, 2*n - 1}] which ...
4
votes
4answers
374 views

Differentiating space curves

I'm trying to do some very basic differential geometry of space curves. For example, a space curve $\gamma:\mathbb R\to\mathbb R^3$ has unit tangent and normal vectors given by ...
3
votes
4answers
3k views

How to write a differential operator in Mathematica

I have a very basic question. I am trying to code the LHS of the differential equation: ...
3
votes
1answer
164 views

Using NestWhileList to determine smallest prime value in series

I have a function recursively defined as follows: $a_{n+1}-1=(a_n-1)\times lpf(a_n)$, whe $lpf(x)$ is the least prime factor of $x$. Now, given an initial value of $a_0$, I would like to find the ...
7
votes
1answer
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: ...
5
votes
3answers
238 views

Creating a nonperiodic function in mathematica

I want to create a non-periodic square wave with values of 1 and -1(not necessarily alternating). For e.g. I want to convert an arbitrary array like {1,-1,-1,1,-1,1,-1} into a function. I tried ...
1
vote
1answer
80 views

Confirming the existence of a function related to a matrix

Is it possible to get an answer to the following question in Mathematica? Let $M$ be a $n$ by $n$ matrix, is there a function $m:\mathbb{N}\times \mathbb{N}\rightarrow \mathbb{Z}$ such that ...
0
votes
1answer
320 views

How could we define a function recursively?

Let us first consider the constructon of the following simple iteration ...
4
votes
1answer
165 views

Downvalues vs. Scoping for Functions

Regarding my recent question on using a default value for a function argument when a pattern was not met yielded some interesting answers, but the general consensus was "Yes this can be done, but ...
3
votes
1answer
2k views

How do I make function A create and return function B?

My basic need is I have to take lots of data and other information and assemble it into a function (static parameters). I then need to call the function many times for numerical results for many ...
4
votes
2answers
186 views

How to achieve Set+Part like behaviour in custom Set function?

So I've been toiling away on my DataFrame package. I've been trying to get Set to work with it, but it seems it either can't be done (ie via ...
15
votes
1answer
412 views

Multiple templates for a single user-defined function

How do I use the ::usage tag to allow the Mathematica v9 front end to know that there are multiple ways to call an overloaded function (a function that can have ...
3
votes
1answer
117 views

Is it safe to assign a variable and function of the same name for different things?

I'm writing out a notebook that goes through the van der Waals Equation of State for gases, and I run into a situation where I want to assign (simplified) Tc[b_]:=5b, use that to solve for b in terms ...
-1
votes
1answer
2k views

How can I make a plot of the Higgs potential?

I was wondering, how would could I make a drawing of the Higgs potential aka "mexican hat potential". I am quite new to Mathematica and don't know where to look to learn how to implement such a ...
6
votes
4answers
794 views

Function argument to default under certain condition

Inspired by this and this question (and how I handle this in practice), what is the best way to default a function value when a certain condition is met? For example, if a function is defined as: ...
2
votes
1answer
279 views

Can my permutations function be defined using iteration?

I have two functions, tuples and perm. They are similar. ...
2
votes
0answers
95 views
3
votes
2answers
170 views

Apply UpValues before Listability

I'm trying to modify Plus but am running into trouble with it being Listable: ...
7
votes
1answer
365 views

How can I define a function that can accumulate its parameter?

For example, write a function add: add[3] return 3 add[4] return 7 add[10] return 17
10
votes
2answers
400 views

Functions that remember their values

Can someone explain what is going on with the following ... func[y_] := func[y] = (Print["Hello world !!!"];) func[1] Hello world !!! ...
1
vote
1answer
653 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 ...
6
votes
3answers
650 views

How can I rewrite this with NestList or FoldList?

The original code used For: ...
4
votes
2answers
799 views

Ways to plot interpolating functions more economically?

I am interpolating a lot of data over geographic coordinates obtained via GPS, and frequently I need to plot these interpolated functions together. For example, I may have an interpolated elevation ...
3
votes
0answers
58 views

How to influence Suggestion Bar in your package/code [duplicate]

Possible Duplicate: Is it possible to customize the Suggestions Bar? I have written a little code (like a minipackage) of different functions. In using my code, the user typically starts ...
1
vote
1answer
339 views

Creating Recursive Sequences

Quite a simple question, I reckon, however, even quite an extensive search hasn't helped me. I want to define a recursively defined sequence that starts with defined ...
4
votes
1answer
182 views

Feedback on my Subscript code

I have written a code, and I need a little feed back.. I want to make the Subscript distributive across (1) addition and (2) multiplication to mimic short-hand for ...
1
vote
3answers
744 views

More than one expression in the Table[] command?

I would like to construct a Matrix using the Table[] command. The issue is that I would like to use more than one expression for it. What I need to obtain is something like this : ...
2
votes
2answers
215 views

Hiding certain user-defined functions in front-end autocompletion

I have written an elaborate code that contains a collection of functions for the user and a bunch of auxiliary functions whose existence I would like to hide away from the user. I've written my code ...
5
votes
2answers
282 views

Pattern matching repeated structures with named subexpression components

I am trying to write a function with a pattern that tests its arguments for a particular structure. But in that pattern I'd like to name a subpattern to make it easier to exract and operate on. The ...
7
votes
7answers
630 views

Can my color function be written more simply?

The code shown below works well, but I think the pure function I'm supplying to the ColorFunction option could be more elegant. How can I simplify it? ...
3
votes
3answers
152 views

How to identify patterns in a tensor-polynomial and replace appropriate symbol?

I want to write a function tensorReplace[input] that takes a tensor polynomial in $r_i$ such as $r_i r_j r_k+r_i q_j q_k +q_i q_j q_k$ , and replaces each monomial ...
2
votes
1answer
171 views

Rookie mistake in defining a function with Modules?

I can't figure out what's wrong with this piece of code. I'm trying to define a function that counts the occurrences of x, y and ...
11
votes
4answers
386 views

Is there a concise form of Which or similar conditional?

Suppose that I want to write a function fun that takes an Integer num as input, and returns ...
13
votes
0answers
176 views

func::usage needs to be run twice? [duplicate]

There is an annoying problem that I can't figure out why it's happening. I have defined a usage for a my function tensorA: ...
10
votes
3answers
389 views

How to set a TraditionalForm output for a symbol

How do I set a TraditionalForm output for a particular symbol/function? In particular I would like my user-defined symbol ...
2
votes
2answers
1k views

Composing two functions in Mathematica [duplicate]

Possible Duplicate: Composition of mappings not working as expected I am new to Mathematica and I am having trouble defining a certain composition of functions. Let ...
2
votes
1answer
264 views

How to override `?NumericQ`

I have a function myFunc which I is to be displayed cleanly if arguments are symbolic, but which can also be numerically evaluated. I do this by defining a ...
5
votes
3answers
1k views

Define an 'inner product' with AngleBracket

I want to define my own little 'Inner Product' function satisfying properties of linearity and commutativity, and I'd like to use the "$\langle$" and "$\rangle$" symbols to output my results. For ...
3
votes
1answer
366 views

Permuting indices to form fully symmetric tensor with repeated indices

I have written a function (version 8) that takes as an input a list of indices such as {i,j,k} and outputs a fully symmetric tensor function containing $p_i$ and ...
2
votes
0answers
95 views

How can this function's options be used in different places? [duplicate]

I wrote this function to make a ListPlot where the points are colored by a third argument. ...
1
vote
1answer
115 views

How do I define a function that, when given a list of parameters, plots a family of functions?

So far I've got this: draw[a_, b_] := Plot[{f[a, b[[1]], x], f[a, b[[2]], x]}, {x, 0, 5}] The function draw will be used like ...
6
votes
3answers
605 views

Defining functions with special cases

I'm trying to define a function myFunc with a special case: myFunc[x_, y_] = (x^2 - y) Log[x^2 - y]; myFunc[x_, x_^2] = 0; ...
9
votes
2answers
906 views

How to create 'help' `?` for a function (as documentation)

I have defined a function foo in some complicated way. But now I would like to add a little documentation that gives the user information on how it is to be used. ...
2
votes
3answers
293 views

How do I construct a pure function to extract data fields from records that are strings?

How can I get from data segment format to the final segment format with a pure function? The data fields are fixed length. There are no separators between the fields. a) list ...
1
vote
1answer
582 views

Combining two pure functions

How to get from the following intermediate result to the final one with just one pure function? ...
9
votes
2answers
378 views

Define Log so that negative reals evaluate on lower edge of branch

I need to get Mathematica to evaluate the logarithm of a negative real number using the lower branch instead of the upper branch, so that while ...