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
41 views

Defining a function with a subscripted head

How can I define a function with subscript? Forexample: f_alpha[x] = 2*x
30
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4answers
1k views

Can a function be made to accept a variable amount of inputs?

I have a function that takes two inputs and processes them for a single output. What I need is one that can take a varying number of inputs. and process them to a single output. Is this possible in ...
2
votes
1answer
68 views

Type declaration for list arguments

How can I make f[n_Integer]=2*n valid for a list of integers? For example: f[nlist_Integer] := 2*nlist[[1]] does not work ...
9
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5answers
309 views

Function for a series of joined slopes

I need a function for a series of joined slopes and my solution feels a bit kludgy. Is there a better way? A list of pairs of transition points and slopes: ...
1
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2answers
47 views

Insert several rows and problem with Return

I wanted to write myself a function that makes it possible to Insert several rows into one list. ...
9
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4answers
231 views

How to Thread with custom functions? Thread vs Map?

This function finds n given the nth prime: findPrime[n_] := If[PrimeQ[n], i = 1; While[Prime[i] < n, i = i + 1]; i, False]; This works: ...
2
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3answers
132 views

Defining a 2-variable function over voronoi diagram

I am new to Mathematica & I am facing a problem as follows: I have created a Voronoi diagram and now I want to assign to each region, a value, i.e., I want to extend this Voronoi diagram to form a ...
6
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0answers
111 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 ...
1
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0answers
69 views

How to Implement a “Function Object” suitable for NDSolve and Finite Element Method?

I have a bunch of methods that shoud return an expression that behave like a function, i.e. an expression that, when supplied with suitable arguments, evaluate to something. A simple ...
2
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1answer
60 views

Working with a two-variable function with one input fixed

Here's what I know how to do: f[x_] := x^2 - 4 x + 4 Ordering[f /@ {1, 2, 3}] This will evaluate f at each point and rank their sizes. Here's what I really ...
0
votes
0answers
80 views

How to make a twice-differentiable function that approximates some data?

I have some time series data that I would like to approximate with a twice-differentiable function. Each time series has ~10,000 datapoints, so I definitely do not want a function that passes through ...
1
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1answer
44 views

Why this isn't a valid argument? [duplicate]

I am having truble understanding why F1 produces an error, since both time and velocity are the same kind of object: ...
1
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1answer
54 views

Change input parameter order in a function

I'm a beginner in Mathematica programming and I'm trying to understand how input parameters work in Mathematica's function. I encountered a problem with the sequence/order of the input parameters of ...
3
votes
3answers
100 views

How to force evaluation on the right of an @ operator?

Is there a way to force evaluation on the right before the Prefix operator (@) without using parentheses? I came across this question when I was working with the ...
2
votes
1answer
38 views

Strange behavior when defining a symbol/function pointwise

I am well aware of the fact that floating point number have finite precision, so one needs to be careful when comparing them. Still, I find it disturbing/surprising that the following input into ...
1
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1answer
108 views

Changing default behavior of Series to give slightly different SeriesData

I am working with complicated expressions expr that contains the symbolic function f[x] which I know to have a pole at ...
3
votes
3answers
1k views

Implementing Newton's method

I have this question on coding Newton's method in Mathematica. I have some code to go by but I have no clue if it's computing the functions in the right order. The book is the numerical methods ...
0
votes
2answers
62 views

Construct a function whose definition depends on the values of its arguments

I have to evaluate the components of a 6x6 matrix $S$. This matrix depends upon the semi-axes of an ellipsoid $a1$, $a2$ and $a3$. For various specific cases (sphere, prolate spheroid, oblate ...
0
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0answers
40 views

Constructing a function for expanding general $n$ products

I have the following quantum mechanically motivated product: $\langle0\vert(A_1b_1 + A_2b_2 + A_3b_3)(B_1b_1 + B_2b_2 + B_3b_3)(C_1b_1 + C_2b_2 + C_3b_3)$, where $b_i$ is an annihilation operator ...
1
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1answer
136 views

Why does Mathematica add Hold to the result of my user defined symbol?

In the code below I have defined a symbol that multiplies two block-matrices (I can't use the builtin Dot since Dot assumes that the matrix coefficients commute): ...
8
votes
1answer
946 views

Stereographic Projection

Say I want to represent points of the complex plane in the sphere $\Bbb S^2$ using stereographic projection. That is, the Riemann sphere: Specifically, it would be nice to be able to: Given the ...
2
votes
3answers
109 views

Problem with the output of a function I program

(This is the function that I programmed) Zm2[Z_, nk_] := (zm2 = 0; For[i = 0, i < Length[Z], i++, zm2 += nk[[i]] *Z[[i]]* Z[[i]];]; Return[zm2];); ...
1
vote
2answers
114 views

Expressions containing globally undefined symbols inside a function where they are defined

Consider the following code. f[a_,b_]:=x; Clear[a,b]; x=a+b; f[1,2] It returns a+b. However, from a certain viewpoint, one ...
3
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5answers
180 views

Converting multi variable expression into a function

So I have this rather complicated looking expression ...
3
votes
2answers
427 views

Using Functions as Arguments to Function

I am trying to make a function like Norm but defined like so: MyNorm[{x_,y_,z_}]=Sqrt[x^2+y^2+z^2]. Mathematica assumes that x, ...
17
votes
2answers
467 views

Using several anonymous functions mixed together

This works: list // BarChart[#[[2]], ChartLabels -> DateString @@@ #[[1]], ChartStyle -> "Pastel"] & This doesn't: ...
6
votes
1answer
253 views

Compiling a function that takes lots of optional arguments

I have a function that takes lots of optional arguments (basically some design parameters, about 10 of them) and performs some basic algebraic calculations involving complex numbers with the options. ...
1
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2answers
59 views

How to generate commands which are very similar?

I have several data sets that I wish to interpolate and integrate like this: ...
32
votes
5answers
1k views

Why is there no PositionFunction in Mathematica?

Too often I have seen the programs of inexperienced users greatly slowed by using Position in an iterative fashion, when far faster would have been to compute a ...
2
votes
2answers
88 views

Need help with code for number theory problem

I'm completely new to Mathematica (used previously only for very simple cases). I need to write a quite complex function. The function must do the following: Input consists of two numbers: a and b. ...
2
votes
1answer
75 views

Generating list of functions from list of expressions

I know how to create a function from concrete expression like Function[{x, y}, x^2 + y^2] But what if I have a list of expressions list1 and I know the set of ...
3
votes
0answers
64 views

How to match the arguments of the function in any order

The issue is the following, with a dumb function with (4) arguments of (4) different heads (for each head is always no grater than one arguments): ...
1
vote
1answer
67 views

Constructing an I-graph

I am attempting to build I-graphs in MMA, i.e. the non-Generalized Petersen graphs, and I found some code from Eric Weisstein, but this is now outdated and doesn't run. I have attempted to switch the ...
6
votes
1answer
133 views

Graphics Function Definition Style (Using SubValues vs. DownValues)

I am going through some of the items in "Modern Differential Geometry of Curves and Surfaces with Mathematica, Third Edition". An example of the style used by these authors is: ...
1
vote
1answer
66 views

Retrieve XML Tree with only specific XMLElements

I would like to retrieve the XML Tree of a XMLObject with only specific XMLElements. In the help of Mathematica ...
50
votes
7answers
2k 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 ...
13
votes
2answers
226 views

Clean and handy Options management/filtering

the case I want to be able to create a function with some default options but also without need to add full explicit list of options available for it. And then inside I want to be able to filter ...
3
votes
2answers
74 views

General function for the expansion of a polynomial of operators

This question is motivated by a Quantum mechanical problem - but in explaining the problem - I assume no knowledge of quantum mechanics. I want to define a function that can expand and simplify the ...
6
votes
2answers
99 views

Optional arguments with lists as function parameter

I'm developing a function f which should support optional arguments {x_, y_} in list form. A simple example looks like this: ...
2
votes
2answers
76 views

Creating a bump function on a spline region [closed]

For a presentation, I'd like to include a 3D plot of a function of two variables x,y with the properties that (a) it looks "smooth" i.e. without jagged edges and (b) has support equal to a given ...
1
vote
2answers
54 views

Subsituting expressions for expressions

I'm trying to define functions using other functions, like so: f[a_, b_] := a/b; a[c_] := c; b[d_] := d; Now what I want to be able to do is two things: ...
3
votes
2answers
89 views

How to use an expression for the argument to a function [duplicate]

I would like to define a function over a list of variables like f[a_,b_,c_]:=a+b+c However, when this list is big it makes uncomfortable to read. Can I somehow ...
0
votes
2answers
69 views

Plotting vectors using derivatives

This question stems from a previous question I asked here: Multiple Integral of equation including dx prime? An equation describing a gravitational field of a cuboid is given as: $V(X,Y,Z) = -G\rho ...
0
votes
0answers
45 views

Multiple Integral of equation including dx prime?

I'm hoping someone can verify I've written this function properly since I'm a little new to Mathematica. What I'm attempting to do is code a function that describes a gravitational field of an ...
2
votes
0answers
50 views
4
votes
6answers
405 views
5
votes
1answer
89 views

Is Sow/Reap compatible with Composition?

I'm trying to figure out why these two pieces of code return different results. As expected, f[Reap[Sow[x]]] gives ...
0
votes
1answer
41 views

How to have default case in Which? [closed]

Saying we have a function: a[x_] := Which[x === 1, "AAA", x === 2, "BBB", _, $Failed] How can I make this function to be equal to ...
8
votes
4answers
1k views

Turn expression into function

I'm new to Mathematica and I spent the last hour trying to make the expression ...