# Tagged Questions

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.

69 views

### NestList and RandomChoice from a list of functions

I am tryingg to modify Chaos Game Fractals from Wolfram Demonstrations. The part I am having problem with is this. Original code: ...
130 views

### IntegerQ returning False despite setting Assumptions

Why does the following not return True? Assuming[z ∈ Integers, IntegerQ[z]] False I tried this on a fresh session of ...
217 views

### How can a function know in which function it was evaluated?

Hello my second question here might be very hard. I am asking for something "magical", if i define a function g and i call it inside a function f, how can g have information about the outer function ...
213 views

### Defining functions when there are a lot of parameters

Suppose I have two lists of parameters: $\delta=\{\delta1, \delta2, …\}$ and $\gamma = \{\gamma1, \gamma2, …\}$. The question is: how can one use $\delta$ and $\gamma$ (the parameter vectors) within ...
68 views

### Supply a function as an argument to another, and find its minimum

I would like to minimize a function, which is supplied as an argument to another function, and report back the estimates of the values of the variables that result in its minimum. In specific, I would ...
74 views

### function definition with a given list of parameters: how to use Evaluate[] properly?

given a list of variables variables = {a, b, c}; I want to automatically define a function f[{a_,b_,c_},x_] := g[a,b,c,x] (...
179 views

### General function taking general number of arguments

The following is an edit of this post, for which a working solution was provided by John McGee. I have a different function and am not sure how to adapt the solution for it: I want to construct a ...
59 views

### Defining functions of varying, iterative numbers of arguments

The following is an edit of this post, for which a working solution was provided by John McGee. I have a different function and am not sure how to adapt the solution for it: I want to construct a ...
42 views

### How to evaluate NMinimize inside a function

I want to define a function that returns a sum of differences of some points to a given function. To obtain these differences I would like to use NMinimize, but if I implement that straightforwardly, ...
273 views

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### Copy Built-in function to new name

It is know that some built-in functions are system function and changing their properties may cause trouble. Suppose for example I want to change features of Cases: ...
50 views

### Mathematica defines a function as list

This might be a very silly question but i'm defining a function as: \[Chi][AR_] := ((AR^(2) - 1)/(AR^(2) + 1)); which is clearly a scalar function of AR; however ...
56 views

### Custom function call does not return a value

I have written the following code to implement a PCA algorithm. It works on standalone basis, however when I put it into a function that is called the following ...
755 views

### Creating the Nabla operator as a operator

How can I define the nabla-operator as a an operator, acting on everything to the right of the operator! Also taking \[Del]^2 would give the second derivivates. I wish to be able to write \[Del]f[...
147 views

### How do I define the following piecewise function?

For 0<=t<=10, if 5t<=n<=5t+2, then f[n]=4n, and if 5t+3<=n<=5t+4, then f[n]=4n+1? I would like then to use the specific values of f[n], for all n between 0 and 54 (t here is any ...
353 views

### Using up-values and down-values

I have a problem I'm trying hard to find a solution for, although I don't know if a solution exists. The following rules produce the result e[2].f[] ...
102 views

### Theory => practice: constructing a function “functionally”

I've read the Mathematica documentation and am certain there's way to do this with functional programming, but can't quite conceive yet how. I've taken a simple example (stating the series for ...
126 views

### Given a list made up of subsets of an alphabet, how can I use associations to create a Boolean dictionary of the given list

I have a list of 30,000 elements, each of the element is a list in itself {{a, b}, {p, q, r}, {a, p}, ..., {z, x}}. Second one contains unique elements ...
108 views

### Table of references [duplicate]

I have a list of variables (say a, b, c, d, e) that I want to assign in a single command. {a,b,c,d,e} = {1,2,3,4,5} would ...
47 views

### Summimg peculiar nestings

I have some lists with peculiar nestings: ...
147 views

### How in Mathematica, would I define a function that takes arguments much like one would in an object orientated language

I would know how to write a function in object orientated language, just I don't know how to do this in mathematica, in an OOP I would define a function like this: ...
53 views

### Retrieve Options from function other than graphics objects

We can retrieve information about used Options for Graphics via: Options[Plot[Sin[x], {x, 0, 1}], "AspectRatio"] (* {AspectRatio -> 1/GoldenRatio} *) even if ...
185 views

### Localising OptionValues

The documentation on OptionsPattern leaves me with some unanswered questions. From the example section: ...
106 views

### Testing for a vector of reals [closed]

Suppose I define: RealVector[expr_]:=VectorQ[expr,NumberQ[#]&&Head[#]===Real)]; Then: ...
60 views

### How to Fold (FoldList) this in a more compact (efficient) way?

Example code: x = Table[something[i], {i, 5}] Table[Fold[f1[#1, f2[#2, a], a] &, x[[i]], {c1, c2, c3}], {i, Length[x]}] This above is just an example. I ...
278 views

### Polynomial expansion of operator

I am new to Mathematica, I am trying to generate the polynomial function of a operator. So for example, the operator $L$ is $\frac{\partial f}{\partial x}+\frac{\partial f}{\partial y}$, and I want ...
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### Numerical Integration/Function

I have a problem with a function defined numerically through an integral of the form: ...
192 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): ...
366 views

### Defining solutions to FindRoot as a function of parameters in Mathematica

This works: f[a_] := x /. FindRoot[x^2 - a == 0, {x, 1}] f[3] (* 1.73205 *) I need this to work, but it doesn't: ...
107 views

### How to input a dynamically changing parameter in NDSolve? [closed]

I am trying to solve a system of DEs with additional conditions, and one condition depends on a parameter. Let us consider the following example: ...
143 views

### Display level of recursion of a recursive function during execution

Given a recursive function, is there some simple way to display or store the value of recursion or "how many levels deep" the function is at a given time? For instance, if we wrote the recursive ...
50 views

### Some problems with complied function

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1k views

I found a nice paper about inverse vector operators here. I have successfully implemented a Mathematica function for most of them, however I can't figure out how to do inverse gradient (page 7 in the ...
164 views

### How to deal with the condition that a function own many options?

Assming that I have a function myFunc which has some options. ...
334 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: ...
85 views

### Forward function arguments to built-in Plot[]

Suppose I need to write a function to plot the real and imaginary part of some function (just an example). I want to define a function foo so that ...
149 views

### Solve returns format I don't understand with dollar sign (\$) [closed]

I have the following function ...
104 views

### The problem (time) caused by ?NumericQ

In here, I asked a related (similar) question. Using ?NumericQ seems have slowed down the entire calculation. But I now have a more serious problem: ...
169 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 ...
80 views

### What are the differences between these functions when used for NMaximize?

In short, the question is how to construct the function you want to optimize? ...