Questions tagged [function-construction]

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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3
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1answer
65 views

elegant definition of piecewise linear functions (spline)

As far as I understand, the Spline object is the result of some approximation or interpolation, it is not for directly defining functions. That's a pity, as that ...
8
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1answer
2k views

What is -(-2,3,4)?

I was trying to define a function f such that, when its second argument is negative, we have $$ f(a,b,c,d,\dots,n)=f(a,-b,-c,-d,\dots,-n) $$ i.e., we reverse the ...
4
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1answer
93 views

Wrong Output in self defined Quaternionic Multiplication

I tried to define quaternionic multiplication in terms of pairs of complex numbers where I identify $\mathbb{C}^2$ with $\mathbb{H}$ via $(z,w)\mapsto z+jw$. Consequently, I used the multiplication ...
0
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0answers
61 views

How to list all the possible functions of given structure?

I can run this command : Tuples[{ Tuples[{x, y, z}, 2], {a, b, c}}] to list all combinations that looks like: ...
0
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0answers
48 views

Iterative loop with many steps

I want to automate the following code, let me begin by explaining the code first. This code, for representation, is divided into 3 parts. The first is: ...
3
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3answers
351 views

How do pure functions differ from functions defined with SetDelayed?

Why is it that f[{{a_, b_}, {c_, d_}}] := (a z + b)/(c z + d) will return (2 + z)/(4 + 3 z) on evaluating ...
1
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1answer
79 views

Defining functions from strings

Blank symbol (_) is moved when applying ToExpression to the following string: ...
3
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1answer
79 views

Generating all connected graphs from a set of n-valent vertices?

I would like to have a function generateConnected[list_] that, given a set of vertices with pre-defined valence (number of outgoing edges) generates all possible ...
0
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1answer
120 views

Table and FindRoot of a two-variable interpolated function

I am having difficulty solving for the roots of the following interpolating function: ...
2
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2answers
83 views

How to make a contextual variable?

I have a question that would be trivial in OOP, but I am a newbie to programming in Mathematica, so I'm wondering how to deal with it. Basically, I want to create a package which basically involves a ...
0
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0answers
24 views

Creating a function in which certain conditions exist

I am trying to create a function for which it is known that certain conditions exist on the argument. I want this to be a simplified version of the function. For example, if I wanted to create a ...
0
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0answers
40 views

Piecewise function to include SawtoothWave function

I am trying to write a Piecewise function that includes the SawtoothWave function. Can someone indicate how to do this, or if it is possible within mathematica? The piecewise code is here: ...
0
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1answer
47 views

Derivative not evaluating when function defined

I have the following code ...
2
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1answer
52 views

How to write down a probabilistic function in Wolfram Language?

How does one write a Wolfram function which has a 25% chance of returning 1, a 50% chance of returning 2, and a 25% chance of returning 3? Here is how the data structure might look like: ...
4
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3answers
170 views

Finding the index of an element to be inserted in a sorted list

I have a sorted list with no duplicates: L = {1, 2, 5, 7, 8} Given an integer n, I want to find the index of ...
2
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1answer
31 views

Setting default function values for particular option values

I have a function with some optional arguments. How do I assign a value for the function when one of the optional arguments takes a particular value, regardless of any other argument values?
1
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2answers
46 views

How to define a function to be used in a loop?

I have written following piece of codes which is a part of very larger program. ...
2
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1answer
82 views

Basic question regarding returning values from user-defined functions [closed]

I'm new to Mathematica today. I would like to write a function that will implement the following pseudocode: f[x_]:= Do something return y I have searched ...
3
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2answers
145 views

Function apply to three dimensions list

I defined a function f[x_, y_] := {x - y, x + y} and I have a list d1 = {{1, 2}, {3, 4}, {5, 6}}; I know how to input ...
7
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5answers
290 views

How to generate all commutative pairings of list elements?

Given a list with an even number of elements, e.g. list = RandomSample[Array[e, 20]]; how can one generate a list of all different commutative pairings of the ...
10
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4answers
187 views

Efficiently merge lists chronologically without duplicates?

Prepare some dummy data to investigate: ...
1
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1answer
36 views

Defining a new function to evaluate a previously defined function at specified parameter set, using fewer inputs? [closed]

I have a function in three variables: f[var1_,var2_,var3_]:=expression[var1,var2,var3]; I want to reduce this to g[var3] and ...
2
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1answer
36 views

Construction of symmetric function / matching function argument patterns

[Edited for clarification after comment] Suppose that the function f is defined as the linear combination of several translated/reflected functions starting from the primitive f0[x,y,z] ...
2
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1answer
51 views

Define a function with specific permutation properties

I want to define a function evaluate[f_[x__]] which acts on an arbitrary function f[a,b,c,d]. The function ...
0
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0answers
29 views

Assign a Derivate to a new fuction variable

I'm having a new problem. I'm trying to create a new function from a Derivate of another function, but i'm can't getting it. Someone could help me? I'm thinking that is something in the syntax of the ...
0
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1answer
32 views

Constructing sequence of function with elements depending on the previous one / recursion

Starting from a function $\theta0[x\_ , y\_ , z\_ ]$, the terms $\varphi[x\_ , y\_ , z\_ ]$ constitutes a sequence of functions that is constructed as follows: Order 1 (one function and its ...
0
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1answer
38 views

Tracking back a variable corresponding to an output

I have a function: ...
0
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1answer
46 views

Preventing an output of a function from being assigned a value

Say I have a function Example[n_Integer]:=n{x,y,z} Example@4 {4 x, 4 y, 4 z} Now, let us assign some values to ...
0
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0answers
20 views

Error while defining custom matrix function

I'm trying to define a custom matrix Ry with a parameter x, in Mathematica. ...
1
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0answers
47 views

Why don't these function definitions work? [closed]

picked up Mathematica (transitioning from Python) a couple of days ago so forgive me for the newbie question. I'm trying to create a function which takes in a list of numbers and returns a list of the ...
14
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2answers
719 views

Flatten not working

I am trying to modify some code proposed here Part assignment is not a symbol and I cannot manage to make Flatten work. I write ...
1
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1answer
79 views

How to pass lists as arguments in NMinimize or FindMinimum?

The following code runs in Mathematica 12. But, I have two problems that I would like to solve: (1) How to pass a list as an argument to the function g in such a way that it can be used seamlessly ...
2
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1answer
30 views

CloudObject when defining functions - how to remove?

I'm an absolute idiot when it comes to Mathematica - I only use it for really basic things (because we use it as a graphic calculator in my high school class), so formatting will be less than ideal. ...
-2
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1answer
31 views
4
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2answers
101 views

Constant Distribution

As far as I know, Mathematica lacks a definition for a probability distribution representing a constant random variable. Is this assertion correct? Is there a problem in making such a distribution ...
21
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2answers
468 views

Custom atomic expressions - modern tutorial

Atomic but sophisticated expressions are all around for a long time: Graph SparseArray. More are coming witch each new release,...
3
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1answer
123 views

Exponential generating function

I need to find the $m^\text{th}$ term for the following expression: $$ \left.\frac{\partial^m}{\partial t^m}e^{a t^2}\right|_{t=0}$$ I computed first few terms and used mathematica "...
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0answers
31 views

Make a function invariant under a permutation of the arguments

The output of my current notebook contains expressions that look as follows (V[{k,q},{s,t}] + V[{-k, -q}, {t,s}]) In my specific application these two functions ...
1
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1answer
78 views

How to use Manipulate in filter design to plot the sum two raised-cosines?

I would like to be able to add a raised cosine to a "standard" raised cosine. With a time delay which I could manipulate (so the shape of the standard cosine function is altered, meaning the function ...
1
vote
1answer
43 views

Issues with negative sign in front of rules for Logarithm simplification

I declare a very simple rule. rule = -x_*Log[a_] :> x*Log[1/a] Now I give two expressions, -x Log[d] /. rule which ...
1
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0answers
45 views

How to simplify Log expressions using rules

I have the following expression, ...
1
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2answers
76 views

Function returning a pattern with condition - how to prevent condition to evaluate prematurely?

I figured it would be convenient to have a function that returns a pattern, that match equally nested brackets, of the specified type. Such a pattern is easy to create, but I get some error messages, ...
0
votes
1answer
55 views

Definition of complex conjugate?

I came across the following way of defining complex conjugate in mathematica [a]: SuperStar[y_] := y /. Complex[u_, v_] -> Complex[u, -v] I am able to ...
2
votes
1answer
66 views

Defining a function that has no return value

How can I define a function with no return value. For example, the Notation function from the Notation package seems to have no return value; I am looking to do the same thing for some of my custom ...
1
vote
1answer
52 views

Why is this NDSolveValue function remembering past inputs?

I have been attempting to generate a function that uses NDSolveValue to return the value of a solution to a system of ODE's when an event condition is triggered, as a function of the initial ...
0
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0answers
23 views

Redefining the inbuilt function and its derivative [duplicate]

I want to redefine the DiracDelta functions and its derivatives. I am successful at redefining the DiracDelta function but not ...
0
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0answers
36 views

Saving DownValues for a function computed in parallel

Is it possible to save DownValues of a function computed using a parallelization routine? I have a rather costly function f I wish to evaluate at a grid and save ...
0
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0answers
50 views

Why is this iterative process with matrix calculation so slow?

I am trying something similar to the following code with Ntime as large as 100 or so. Now it's very slow as shown by the Ntime=3 ...
0
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1answer
61 views

Memoization (or otherwise) for a recurrent definition of a (double) sequence of functions

Beside I've found answers to similar questions (e.g. this), I can't adapt them to my case. I am interested in the following sequence of functions $p_{m,n}(t)$, where $m$ and $n$ are integer: $$ \...
2
votes
1answer
38 views

User Implemented SHA-1 is failing for strings of length >512 bits

So, earlier, I posed a question regarding getting a user implemented SHA-1 hash function to work correctly. Well, I fixed the problems, cleaned it up a little bit, but now I have the problem for when ...