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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2
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0answers
91 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
109 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 ...
5
votes
3answers
428 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; ...
5
votes
2answers
404 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
277 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
458 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
329 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 ...
1
vote
2answers
206 views

Function with different set of arguments [duplicate]

Possible Duplicate: How to create functions of arbitrary number of variables? i want to use a Function f[] with different set of arguments. example: ...
4
votes
2answers
188 views

How can I improve this trial division procedure?

My background is procedural programming, so I find this construction quite natural. Is there a way to get rid of the While? ...
4
votes
6answers
226 views

Filter list with different list in it

I have a list like: {{{4, 14}, 1}, {{4, 15}, 1}, {{4, 16}, 1}, {{4, 17}, 1}, {{4, 18}, 1}, {{4, 14}, 3}, {4,15}, {{4, 16}, 2},{4,18}} Now I want to ...
3
votes
1answer
253 views

Evaluating a function on permutations of its arguments

Say I have a function "temp" of $n+1$ variables, $y,z1,z2,z3,...,zn$. I want to test if my function has certain symmetries like swapping $y$ with square of any $z$, swapping any two of the zs, ...
1
vote
2answers
195 views

A function that only evaluates on lists of pairs [duplicate]

Possible Duplicate: Why doesn’t PatternTest work with Composition? I'd like my function to only evaluate when the argument is a list of pairs. It seems like ...
0
votes
2answers
229 views

How to use Solve rules as a function body?

Solve gives me an expression which I want to use as the body of a function. Rather than run Solve every time inside my function ...
14
votes
2answers
241 views

f[arg1, arg2,…,argN] vs. f[{arg1, arg2,…,argN}]

I am trying to reproduce the API of a function (written in R) that accepts an arbitrary number of arguments and handles it the same way as it would handle a single argument that is a list of different ...
2
votes
1answer
192 views

How do I determine if there's an arithmetic sequence within a list? [duplicate]

Possible Duplicate: find subsequences of constant increase Given an arbitrarily long list of integers (let's say they are sorted), how would one determine if any 3 (or more) of those ...
20
votes
5answers
464 views

Can I make a default for an optional argument the value of another argument?

I'd like to define a function with several optional arguments, some of which default to the value supplied for other arguments. For example, I'd like to be able to write something like ...
2
votes
1answer
154 views

Difference between function definitions [duplicate]

Possible Duplicate: Functions vs. patterns I thought about describing the context in which I faced this problem, but I figured it is general enough and clear enough to pose it as it is. ...
8
votes
2answers
3k views

How to define a differential operator?

I have a linear differential operator, for instance, $L\left (\partial _{t} \right )=\partial _{tt} - 3\partial _{t} + 2$. I use it in 2 different ways: apply the operator to a function: $L\left ...
-3
votes
2answers
256 views

How to correctly call a Module within another Module?

How to embed and call the correct embedded modules inside another Module? Say: ...
6
votes
3answers
681 views

How do I designate arguments in a nested map?

Say I have two lists, list1 = {a, b, c} list2 = {x, y, z} and I want to map a function f over them to produce ...
-1
votes
1answer
467 views

Multivariate Function Approximation With a Large Dataset

I have a nice amount of data from a trading strategy I am working on, where I have two different liquidity parameters as x, y variables. Before entering a trade I am taking the moving average of ...
17
votes
2answers
384 views

Pattern that matches colors

Suppose I'm writing a function that takes a color as a parameter; for example: drawShape[color_] := Graphics[{Style[Disk[], color]}]; But if the caller inputs an ...
5
votes
2answers
167 views

How is OptionsPattern[] defined? Can I replicate this?

I am writing several functions which all take similar input parameters (a complicated nested list structure). Is there some way for me to define a pattern that can be used in multiple places and ...
1
vote
1answer
193 views

Find the derivatives of arbitrary order of a function found using NDSolve

For the following initial value problem BC[b_]:=x[0]==b; eq[b_]:=NDSolve[{equation==0, BC[b]}, x, {t,0,1000}]; body[t_,b_]:= x[t]/.eq[b]; one could define the ...
1
vote
1answer
93 views

Why function is evaluated backward?

I have a simple function: f[x0_,y0_]:= Module[{x=x0,y=y0},For[i=0,i<2,i++;Print[x],Print[x+y]];] So when I call it: ...
2
votes
3answers
510 views

Generating pairs of additive and multiplicative factors for integers

Given an integer $n$, I want to get two lists: a) the set of pairs of the divsors $a,b$ into exactly two factors $n=a\cdot b$, b) the set of pairs $a,b$ of two summands $n=a+b$. The code I ...
2
votes
0answers
363 views

Generating a function which outputs possible chemical reactions

I want to make a list of chemical reactions and I write them down in a $\require{mhchem}\LaTeX$ format. They are of the following form $$NA_n^i+MB_m^j \rightarrow \hat NA_{\hat n}^{\hat i}+\hat ...
1
vote
0answers
257 views

Return Functions from parallel execution of module

I wrote a module which numerically solves an ODE using NDSolve. The result from this is e.g. either ...
0
votes
1answer
109 views

Defining functions from expressions of variable lengths

I have a list of symbols that I have defined using d = Table[Symbol["d" <> ToString[i]], {i, 1, n}] giving ...
7
votes
2answers
3k views

Building matrices by attaching vectors (columns) and matrices

Having the need to attach a column to a matrix or to join matrices to make longer rows is an operation that I use very frequently and I find the Join function ideal ...
1
vote
0answers
86 views

Non Commutative Multiply [duplicate]

Possible Duplicate: Non-commutative symbolic linear algebra I want to multiply two matrices, for example, A = {{e, f}, {g, h}} B = {{a, b}, {c, d}} ...
1
vote
1answer
642 views

Matrix Multiplication Modulo 2

I would like to perform matrix multiplication modulo 2. Hence, instead of the usual: A.B I did: ...
0
votes
1answer
184 views

How to generalize a formula?

This is a piece of my code: ...
0
votes
1answer
133 views

Bad function evaluation

I am having some trouble with this function ...
3
votes
4answers
230 views

How to create a composite function from a variable number of components?

Background of the problem: A patient takes a drug every $X$ hours with a half-life of $Y$ hours. How much of the drug will be (exactly) in his system after $h$ hours? For $X=24$, and $Y=24$ I made the ...
2
votes
1answer
132 views

Implementing a For (?) or series or loop (?) for individual results for every x to n

I'm working on improving a modeling formula and have spreadsheets worth of data to use, but my work so far has been quite tedious. I'm essentially pulling 20 rows of data from each separate sheet of a ...
1
vote
3answers
822 views

Better solution than returning a list of 3 values?

I have a function (using SetDelayed) that currently returns 3 values in a list. Later on I use the result of this list along with ...
2
votes
1answer
261 views

Defining a function that handles Dynamic arguments similar to Built-ins

Firstly please note that I'm using simply Dynamic behavior to illustrate my question, I'm not asking how to move a Disk or make ...
2
votes
2answers
103 views
1
vote
2answers
150 views

How to mix Unevaluated property of function arguments with expression assignments?

This is a follow-up to my (solved) question How to distribute a generic function of two arguments (without evaluating the arguments) Say, I have a binary function ...
4
votes
3answers
198 views

How to distribute a generic function of two arguments (without evaluating the arguments)

I guess there is an easy way to do this, but I can't seem to figure it out. What I would like to do is to distribute a generic (i.e. without specifying what this function really does) binary function. ...
7
votes
3answers
356 views

Composition of mappings not working as expected

I have two functions $f,g:\mathbb{R}^2 \to \mathbb{R}^2$ and I define a third one $h:\mathbb{R}^2 \to \mathbb{R}^2$ as the composition $$h(x,y) = g(f(x,y))$$ I'm trying to get this function into ...
4
votes
2answers
371 views

Define product derivative

How do I define the $n$th product derivative of a function in Mathematica? The first product derivative $f^\ast$ of a function $f$ is $$ f^\ast(x)=\exp\left(\frac{f^\prime(x)}{f(x)}\right) $$ The ...
3
votes
3answers
434 views

How to pull scalars out of a function that should act on lists?

Suppose I have A = a vecA B = b vecB where a and b are supposed to be arbitrary scalars ...
2
votes
1answer
154 views

Specifying form in MemberQ

This seems like a very simple question, the answer to which should be obvious to me. So I won't be offended if this question is closed. But I'm having trouble figuring out the answer. I would ...
4
votes
2answers
207 views

Function to select a row whose kth element is closest to a given number

I'm trying to write a function that picks out the row of a Matrix whose kth element is closest to some given number that will be given to me. So for example, ...
14
votes
1answer
305 views

Modules that initialize themselves on first call

I use a lot of functions that extract a specific data item from a file with many data items. I want these functions to load data (slow) and return the item (fast) on first call, but just return the ...
11
votes
2answers
965 views

NestList on a function of several arguments

I'd like to know if it is possible to use NestList on a regular function of several arguments, such as: ...
5
votes
2answers
3k views

How to find (numerical) value of a derivative at point?

I have the following function: f[0, 0] = 0 f[x_, y_] := Exp[-(x^2 + y^2)^(-1)] How do I find its partial derivatives at any given point, including $(0,0)$? This ...
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: ...