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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0answers
25 views

Applying a function to the second element of a list [duplicate]

I'm trying to apply a simple function to the second element of a list: {#1, #2/5} &@{1, 2} But this returns an error message. ...
0
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1answer
28 views

Using the Function construct in a table with parameters [duplicate]

I'd like to define a table of functions like so Table[Function[{x,y},{x + k y,x - k y}] , {k,1,10}] My intention is to have the first function defined with k=1, ...
1
vote
1answer
46 views

Is there a way to make the Function construct accept a list as argument? [duplicate]

Is there a way to make the Function construct accept a list as argument ? Writing Function[{x,y},{x+y,x-y}] does not work, ...
3
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0answers
103 views

Obtaining a Previously Constructed Function as Desired Output

I was playing around with some Generalized Trigonometric Functions defined as follows; ...
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2answers
52 views

Importing data, then plotting ListPlot. What's the most efficient way to write a code?

It should be a boring question to ask for someone, but this is very basic need which I haven't resolved by myself. I know I can use MapThread and pure function to make it short and beautiful, but even ...
1
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1answer
51 views

Using the Nest function — Confusion on my output

I have the following code and output where the original function is $f(x,a) = a^2 - x^2$. ...
0
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1answer
41 views

Convert string to function with an argument

I am trying to build an expression by first writing it out as a string and then using ToExpression to convert it to an expression. However, I cannot figure out how to make expression recognize x as an ...
2
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0answers
47 views

First position of incremental series

I am still a beginner and maybe I want to do something too complicate! After 29 cycles I obtained the following events list: ...
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2answers
71 views

Problems using a function as an argument

I made a function: f[x_]:=x^2+1 and when i use it on, for example f[5], i get the answer 26. . But when i use it on: PollardRho[a_, f_] := Module[ {}, Return[f[a]] ] And when i write ...
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3answers
230 views

How to create a version of FixedPointList for asymptotically periodic functions?

I need to efficiently generate a bunch of bifurcation diagrams. A simple familiar example illustrates the efficiency problems I'm running into: ...
1
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0answers
47 views

NonLinearModelFit to a Function [closed]

I have a multiple dimension function that is fairly complicated. Instead of simply using Series to get a taylor series of the function, I would rather specify my ...
1
vote
0answers
77 views

Pattern for a function of say 2 variables [closed]

How can I specify a pattern for an expression f for which say f[x,y] returns a value, ie is defined as a function taking two ...
1
vote
1answer
145 views

How can I implement a moving standard deviation for a time series?

I imported the following dataset and converted it into a time series. ...
0
votes
1answer
44 views

Call user defined function from many notebooks [duplicate]

I wanted to ask a simple question. I am new to Mathematica, and I don`t find a way to call user defined functions just as I call Mathematica functions. I want to use my own defined functions, but ...
1
vote
1answer
80 views

Double arguments and place of the underscore

Could someone explain me of this bit of code below is correct: Is it possible to define a function with a second bracket, see below, i.e. f[x_][y_]? And what does ...
3
votes
2answers
249 views

Handling options in my function [duplicate]

It seems this should be easy, by I just can not figure out how. I'm making many very similar style plots, so I want to make a function with all the default options specified. Sometimes I need to tweak ...
6
votes
2answers
110 views

How to define a complicated function inside the body of Compile?

I want to compile a function in a way to keep its memory footprint down. In the example below, I am trying to compile a function f that makes three calls to ...
1
vote
2answers
79 views

What's the easiest way to remove overall factors from polynomials?

I have code that outputs polynomials (in #1) such as the ones below (note that the trailing Function character ...
8
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6answers
267 views

Combinations of multiple matching patterns

I wonder if there is any nice way to combine DownValues (or any other suitable rule-/pattern-/function -based Mathematica construct) when multiple patterns match an expression. Let me explain what I ...
9
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1answer
139 views

Maximizing a recursive functional equation

I would like to maximize a recursive functional equation but I am struggling with setting up the problem correctly. The equation I am interested in captures the nature of a decision process over time ...
0
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1answer
48 views

Simple grouping equations [closed]

I'm new in the Mathematica world. A very basic question. I have been using the command Eliminate on a set of equations as follow: ...
4
votes
1answer
104 views

Are these two functions equivalent?

I checked several cases and saw that two functions are equivalent in these samples. However, are the two equivalent in all cases? Is there a way to check that? Explicit function: ...
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2answers
63 views

Evaluating While Loops inside Modules [duplicate]

I am trying to compute some objects inside while loops within modules, but I keep getting the following error: ...
1
vote
1answer
45 views

Construct all possible sets of pairs [duplicate]

I am looking for a nice way of constructing all possible pairings of a given list. Currently I am using the brute force approach of sieving the 2-partitions of all permutations. ...
3
votes
1answer
113 views

The basic primitive recursive functions

How can the basic primitive recursive functions be expressed in the Wolfram Language? Apparently here's an example for primitive recursion: ...
0
votes
1answer
48 views

How to define InterpolatingFunction on a variable set of points?

I would like to define an InterpolatingFunction to which data points are transferred as a parameter, e.g.: ...
4
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2answers
55 views

Is it possible to match a sequence with multiple heads without using Condition

Suppose I have: expr = Times[2, a[x,r], a[y,1], c[z,0,0], d[w,m]]; If I want to match a sequence of expressions with the same head ...
4
votes
2answers
161 views

Subset-type function construction

This is probably a very straightforward thing I am missing, and probably also a duplicate(!), but I can't for the life of me think how to do this cleaner. I want to achieve what ...
4
votes
1answer
89 views

Pertubation series of given equations

I would like to define a function that does the following. If I have an equation, for example: $$f(x)+[1-f^2(x)]+f^{\prime\prime}(x)+f(x)\ f^\prime(x)=0$$ and I am given a value for $f$ to expand ...
0
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0answers
75 views

How to change the built-in function? [duplicate]

As you can see,the original Differences will get {} when your parameter is a list with one element just. Differences /@ {{1, 2, ...
4
votes
2answers
85 views

Finding the smallest starting number producing a Collatz sequence of length 125 which ends with a value > 4

I'm supposed to do a Mathematica function that selects the smallest number not less or equal to 4 after 125 iterations. I am not good at coding, so some help/advice would be awesome. My code so far. ...
3
votes
2answers
47 views

How to add Optional Sequence

Note: This question could be duplicate but I couldn't find any so far. It is know that Optional (:) can be use to represent expression if omitted. ...
0
votes
1answer
50 views

Cumulative function definition and plotting [closed]

I'm quite new to Mathematica. I have an issue defining cumulatively a function. Let's say I have a waveform f[t] , and I want to create a function with many copies ...
0
votes
1answer
61 views

Should I define a function or not?

I was trying to execute the following code: ...
-1
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2answers
83 views

Gradient of interpolated 3D data in mathematica 9

tt = Flatten[Table[{x, y, z, btot[x, y, z]}, {x, -1, 1, 0.1}, {y, -1, 1,0.1}, {z, -1, 1, 0.1}], 2]; ff = Interpolation[tt] Till here it is working fine as it is ...
4
votes
1answer
140 views

How to efficiently write code with many functions that have variable number of iterators/arguments/

I am finding myself having to code functions like this: $$\text{answer} = \sum_{k_0 = 0}^{\color{Blue}n_0} \sum_{k_1=0}^{\color{Blue}n_1}\cdots\sum_{k_{N-1}=0}^{\color{Blue}n_{N-1}} ...
8
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4answers
278 views

How to inject unevaluated list of Unique into a RuleDelayed?

I am writing a function that constructs a rule which has Unique[] in the RHS. Here is a simplified segment of code ...
4
votes
2answers
85 views

How to Return $Failed symbol in a MakeBoxes context?

Three months ago, I asked a question about How to build a function object like the built-ins? Today, I used a solution proposed by István Zachar ...
0
votes
1answer
46 views

Results of a function are different when the function call and subsequent statements are evaluated one line at a time

I have some code that I am porting from VBA to Mathematica. The original code processes data on an Excel spreadsheet. In Mathematica, I find it convenient to replicate the Excel spreadsheet data ...
7
votes
1answer
131 views

Can one specify a “computed optional value”?

I would like to write a function with an optional argument, which if absent should not be a default value, but rather a computed value. What I mean is the following [warning this code does not work, ...
3
votes
1answer
77 views

Finding all Spanish words with given vowel patterns

I'm trying to implement a function using DictionaryLookup that does the following: Uses a Spanish dictionary Lists and counts of all words where the 5 vowels ...
8
votes
1answer
95 views

How to make `D` apply chain rule on user-defined symbols as it does on `Dot` and `NonCommutativeMultiply`

I have my own version of Dot called mydot, and it behaves quite similar to the built-in version in that it represents the ...
2
votes
1answer
35 views

Expanding/printing function with constrained arguments [duplicate]

Let's say you have a function $ f(t) = t, \text{ for } t > 0,$ declared in Mathematica as f[t_?(# > 0 &)] := t; How do you print that function? I ...
1
vote
1answer
94 views

Continued fraction with different numerators [duplicate]

In Mathematica, is it possible to form the continued fraction of the following formula? $$ f = a_1+\cfrac{b_1}{a_1+a_2+\cfrac{b_2}{a_2+a_3+\cfrac{b_3}{a_3+a_4+\cfrac{b_4}{a_4+...}}}} $$
8
votes
4answers
205 views

Identify the independent variable in an expression [duplicate]

Suppose that you write something like this for your students. This is just the beginning of something I would like to write to help them with the formal definition of a limit, but I am puzzled by the ...
2
votes
2answers
121 views

Plotting a function defined to be infinite over a sub-domain [duplicate]

I'm trying to plot the following function with the constraints shown, $$f(x)=\begin{cases} \infty \quad x<0 \\ A\,x\quad x\ge 0 \end{cases}$$ However I can't work out how to show this in ...
7
votes
4answers
99 views

Problem with handling a factor of $1$ in pattern matching

I am trying to implement the creation and annihilation operators $\hat{a}$ and $\hat{a}^{\dagger}$ of quantum mechanics with the following code, but alas, there is a problem with the pattern matching ...
9
votes
2answers
921 views

Number of digits for factorial of 12345678987654321

What is the number of digits (IntegerLength) of the factorial of 12 345 678 987 654 321? The number of zeros at the end of this factorial was calculated and it is huge: exactly 3 086 419 746 913 569 ...
5
votes
1answer
125 views

How to make my fuction return a step count

I am new to mathematica, and I have this 3d random walker program which runs with a fixed (given) amount of steps. What I want it to do is to run forever but stop when two walkers collide (aka have ...