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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6
votes
2answers
280 views

What evaluation mechanism is behind Mathematica support for multiple definitions of a function? What is the benefit of this?

I am studying the question What are the most common pitfalls awaiting new users? Up to now, I have fulfilled some of the parts but yet don't understand which this problem is related to? Consider the ...
2
votes
3answers
185 views

data manipulation in log-log scale

Say that I have the following: y[t_] := 2 + (2/10)*(1 - Exp[-t/11]) timedat = N[Table[{t, y[t]}, {t, 0, 10, 1/1000}]]; How is it possible to construct an ...
0
votes
1answer
88 views

Optimization of a voxel projection function

I implemented a function to check if a voxel (3D pixel) is well projected on the space of a image (black and white silhouette) through a perspective camera. The function does the work but It need more ...
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 ...
0
votes
1answer
70 views

a function that evaluates a Section

I have defined a function that returns different output according to the values of the axes of an ellipsoidal. The function is given below: ...
4
votes
2answers
109 views

Unsure how to nest / fold this power tower factorisation

Not quite sure how to nest this. What I would like is power tower of integer factored until all powers are primes. eg desired output for f[3*125^4] would be ...
2
votes
0answers
36 views

Unexpected behavior from Return called in a Block [duplicate]

I like to write functions that dispose of failure cases early, before they do the main calculation, but I don't like to write cascading If statements. Here is a toy ...
16
votes
1answer
682 views

Lazy lists of Tuples and Subsets

I'm trying to build a lazy list that evaluates the n'th m-tuple or subset of a given list using Mathematicas ordering without calculating all the Tuples. The purpose is to allow for example the ...
1
vote
1answer
67 views

Writing a function with two functions as arguments

I am trying to write a function of two functions. A function of one function works as in h[f___, x_, y_] := Integrate[f, x] h[x^2 + y, x, y] and this ...
9
votes
1answer
178 views

Finding large prime gaps

I am using basic searches for prime gaps as follows: ...
2
votes
3answers
92 views

Making a list of functions

Suppose I have the following equation system to solve: x(t_):={x1(t),x2(t)}; DSolve[x'(t)==x(t),x(t),t] This code works fine, but now suppose that instead of 2 ...
12
votes
4answers
214 views

Distributing function arguments with function compositions. How to compute $(f + g^2)(x) = f(x) + g(x)^2$?

Suppose I have two functions f and g. To compute $f + g$ evaluated at a point $x$, I know that one can use ...
17
votes
3answers
471 views

Improving speed of code computing number of nonrepeating partitions

I need to answer the following for a number of parameters: How many ways can the integer $k$ be written as a sum of $n$ different integers ranging from $1$ to $m$? My initial attempt was the ...
2
votes
1answer
218 views

Issue with Coefficient command [closed]

I'm trying to used the Coefficient command to extract the numerical values in front of a Chebyshev polynomial. I know that there is a numerical way to do this, presented in numerical recipes, which I ...
0
votes
1answer
75 views

Working with functionals [closed]

I am trying to work with functionals in Mathematica, this means that I want to define a function of a function. I defined my function of a function as: ...
1
vote
2answers
52 views

Replace function with multiple functions while respecting the inputs

I want to replace a function with either one or two functions and also combine their arguments. Say I have an original expression expr = u[i + 1] r[i] r[i-1] ...
3
votes
5answers
306 views

Function involving For loop

I've written the following function (the code includes the output): ...
4
votes
2answers
241 views

Generate the Fibonacci sequence with Accumulate

Is there a way to generate the Fibonacci sequence with the Accumulate function?
3
votes
2answers
135 views

Symbolic multiplicative partitions

Let $p_n\#\equiv\prod_{k=1}^{n}p_k$ (primorial): p[n_] := Times @@ Prime[Range[n]] then the multiplicative partitions of $p_{1,2,3,4}\#$ are $$ \{\{2\}\},$$$$ ...
0
votes
0answers
56 views

Is there a IsDefinedQ function? [duplicate]

I have a function which is a bit expensive to calculate. I want to translate and integrate. I want to translate by values on a grid, store the values of the integral and refine the grid. That is, I ...
2
votes
1answer
65 views
6
votes
2answers
112 views

Force evaluation of the right-hand side of a local variable definition

One can do expression = a + 1; f[a_] := Evaluate[expression] but how would one do something like this ...
6
votes
2answers
153 views

How to specify and use nested options for a function?

I want to write a function that takes options that are nested. For example, suppose the function has one main option, "method" which can take two values, "a" and "b". Also, when method is "a", it can ...
0
votes
0answers
103 views

Best practices for breaking up functional blocks?

Say I have a main function that does some job, and I'm only interested in the final result of ans, i.e., the local functions are not important and produce no ...
-1
votes
4answers
106 views

Converting an expression to function [duplicate]

I have the following problem. I current can automatically create the variable positionPayload, for instance: ...
0
votes
1answer
100 views

Replacing the Slot in an expression

So I've got Mathematica to handle the grunt work for me to obtain expression: Root[ (* blah, blah *) + #^2 + (* etc, etc *) ] Now, the value inside Root is a ...
4
votes
1answer
117 views

Substitute a function's definition for its name

I'm having trouble with a function which is supposed to work on another function. Simplified version: ...
3
votes
2answers
73 views

How can I adjust the global input variable of a function to the value of a local variable within the function

I am trying to define a function f[l_] that will perform an operation on whatever input variable I use (normally I use l which ...
1
vote
2answers
54 views

How to define a function `deriv[f[x]]` such that its output is an unevaluated expression `fx=D[f[x],x]`?

I want to define a function deriv[f_[x_]] such that when I run deriv[f[x]], the output is an unevaluated expression ...
0
votes
2answers
60 views

Function to list Collatz sequence doesn`t work [duplicate]

I am new to Mathematica and was trying to make a function that lists the Collatz sequence stating with a given number, but I can´t get it to work. Here is my function: ...
8
votes
2answers
3k views

Gram-Schmidt Process for Polynomials

I want to implement the Gram Schimdt procedure to the vector space of polynomials of degree up to 5, i.e. I want to find an orthogonal basis from the set of vectors $v=(1,x,x^2,x^3,x^4,x^5)$. The ...
1
vote
1answer
151 views

Defining a derivative on a custom function

I am trying to define a derivative that acts on a custom function, $f$, such that when it acts, it increments one of the arguments of by 1. f is not defined; I just want to use it to keep track of ...
2
votes
1answer
63 views

Dropping rational coefficients

I have a list of expressions (they all are exact numeric quantities, not containing any variables), some of them have integer or rationals coefficients, or complex coefficients with rational or ...
1
vote
3answers
123 views

Setting ::usage for variables returned from a function

What is the best way to achieve {v,u} = f[]; (* Returns value and usage description *) v::usage = u; from inside f, i.e., ...
2
votes
1answer
61 views

Manipulating unevaluated expressions in nested function calls

This is a follow-up to my earlier question: Passing an unevaluated part of an association to a function I'm trying to create a modular dashboard that controls sound volume of an audio system ...
3
votes
1answer
401 views

NestList with a list inside?

I'm new to Mathematica, and was looking for more efficient ways to implement the Do loop below. a, ...
36
votes
2answers
1k views

Variable naming changes everything

Bug fixed in 10.0.0 I am having a rather unusual problem I do not understand with Mathematica where renaming one of the variables of my function causes the function to stop "working". Here is the ...
2
votes
1answer
211 views

How to get numerical results from HeavisideTheta?

I have defined a table tab = {7.52521, 17.0083, 22.5678, 11.8707, 8.27799} and a function ...
1
vote
1answer
100 views

Min function for functions f1, f2, [closed]

There are several "min" functions in Mathematica. In the "Numerical" category, there is a "Min" function that works on a numerical list. Then there's MinValue for finding the minimum of a whole ...
0
votes
0answers
40 views
3
votes
1answer
145 views

How can you get the area of a region from an image?

Suppose we have a square of side "L" m, How can I calculate the hatched area, if the corners of the square are centers of circles. It can be generalized to any region? edit: This is the result I ...
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 ...
2
votes
1answer
53 views

Appending Delayed Evaluation

I have a function that need to be summed over all parameters given in a separate list. f[x_,y_,z_,n_,i_]:= (*Some function*); list={{n1,i1},{n2,i2},...}; I need ...
2
votes
2answers
197 views

Multiply pure function with scalar

Somtimes I still get lost in the Hold, HoldAll etc. functions of Mathematica. I want to scale a simple PDF function with a previously calculated variable e.g. ...
0
votes
1answer
50 views

Finding function by constraints

I have the following coefficient finding problem: f[x] := a * Log[b*x + c] + d Constraints: f[0] = 1 f[80] = 0.5 I want to find the coefficients of f that ...
1
vote
0answers
59 views

function of a function [closed]

I have the following two functions, 'f' and 's': ...
31
votes
1answer
618 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 ...
10
votes
4answers
411 views

How to check the style and number of arguments like the built-in functions?

Given that I have a function sqrt[x] that I must check the style and number of argument x. I can do like this: ...