Questions about the use of built-in Mathematica functions, including pure functions.

learn more… | top users | synonyms

9
votes
2answers
275 views

What does IndexBy do and how exactly does it work?

I just saw the function IndexBy in the autocomplete suggestions and I was curious to know exactly how it works. Unfortunately, there's no trace of it in the ...
1
vote
1answer
83 views

How to construct a kernel from a function?

I would like to convolve an image with a mathematical function. I understand that I need to have the mathematical function in a matrix form. How can I build it? Thanks
2
votes
2answers
107 views

Creating a Cayley's table of square

I'm interested in creating a Cayley's table of square using Mathematica. I'm not a programmer but occasionally resort to using Mathematica to simplify my work insofar as the programming doesn't take ...
1
vote
1answer
104 views

Understanding `FixedPoint`

I understand that FixedPoint[(# + 2/# )/2 &, 1.] can be written ...
0
votes
0answers
26 views

Fibonacci series up to 300 terms [duplicate]

I tried to generate a list of Fibonacci numbers up to 300 terms and gets a runtime error. f[0]=0; f[1]=1; f[x_]:=f[x-1]+f[x-2]; Table[f[x],{x,1,300}] Is there ...
0
votes
1answer
52 views

Question about a catalytic equality?

I have a question on math.SE that explains how I came up with these equations. ...
-2
votes
3answers
65 views
3
votes
1answer
78 views

Why minimization does not work with symbolic array as arguments

If I try to minimize with constraints a function of several variables, with Gamma regularized function involved in the constraints it seems to works, as shown below (this is just a dummy example ...
-3
votes
2answers
89 views

Random Polynom Plot [closed]

I should write a module "RandomPolyPlot[n, amin, amax]" which calculates all roots (nulls) of a n-th degree polynomial function. Then I should illustrate it on the complex plane. I also should ...
1
vote
2answers
80 views

How to stop FullSimplify from returning Root objects

I have several expressions in a series, such as 1/4 (-(1/4) + Sqrt[5]/4 + I Sqrt[5/8 + Sqrt[5]/8]) (-1 - Sqrt[5] + 2 Sqrt[7/2 + (5 Sqrt[5])/2]) If I run ...
-3
votes
2answers
92 views

Write a function, write a pattern [closed]

I have the following list: list = {{1, 2, 4}, 6, 7, 8, {8, 2}, {3, 4}, {4, 5}, {1, 2, 3, 1}}; (a) I should write a predicate-function in combination with an ...
0
votes
0answers
28 views

Why don't we use SetDelayed when we use placeholder to declare a function? [duplicate]

On the answer of http://stackoverflow.com/questions/4272067/what-does-mean-in-mathematica Typically when we declare f(x)=x^2 function, it is: f[x_] := x^2 But ...
0
votes
0answers
40 views

How can I put the results of TrigReduce function into a more convenient form? [duplicate]

a1 D11 Cos[n x] + a0 a1 D11 Cos[n x] + 1/2 a1 a3 D11 Cos[n x] + 1/2 a2 a4 D11 Cos[n x] .......for example this expression can be written like ('expression') * ...
6
votes
2answers
100 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
1answer
117 views

How to run code in a saved file when it is opened

I have a Mathematica file that I saved. In it, I have multiple functions that I've defined and have evaluated a number of the functions with different arguments. I would like to be able to open the ...
1
vote
1answer
68 views

Defining a Function

I've been reading about functions in Mathematica and playing with this for hours, but I'm clearly missing something. The following code correctly calculates "fail", the number of failed scenarios. I ...
1
vote
1answer
212 views

Create a function with Dt[x] as a variable

I have a function (for example F[x_]:=Cos[x]). I want to define a function like Fdot[x_,xdot_]:=Dt[F[x]] where xdot represents Dt[x]. For example, to define Fdot one might naivley try ...
2
votes
1answer
129 views

How do I download and export data from many weather stations?

I tried this code, which downloads data from several weather stations. ...
1
vote
0answers
32 views

Import names into notebook namespace

I have function that at some point has list of strings (e.g. {"apple","pear"}) and I want to declare (initialize) those variables in notebook namespace to default value (e.g. 0) so I could execute in ...
0
votes
1answer
127 views

How can I use nonlinear model fit with multiple variables? [closed]

I have a data set with four entries. the first three entries correspond to variables in the fit x,y, & z. The fourth entry corresponds to the function value. I am trying to fit this data to a rate ...
0
votes
1answer
72 views

How to properly use conditionals inside NDSolve

Currently I am working with Mathematica to learn the program, and I'm confused what exactly is wrong with this code. ...
0
votes
0answers
44 views

StringLength function [duplicate]

allWeatherStations = WeatherData[]; fullformStations = FullForm /@ allWeatherStations; Tally[StringLength /@ fullformStations[[All, 1, 2]]]. This code not working. ...
-1
votes
1answer
133 views

need help to price a european option using finite difference method [closed]

I am writing a function to price European option using backward induction finite difference method. The function is expected to price a European option taking Stock (stock_), age (time_), volatility ...
19
votes
5answers
2k views

Moving maximum function?

How can I construct a moving maximum function? For example, if I have a list of 12 values: { 5, 6, 9, 3, 2, 6, 7, 8, 1, 1, 4, 7 } and I want to maximize over 3 ...
0
votes
1answer
52 views

Replace element of matrix based on rule which invloves other element of same matrix

I am trying to replace 1s row of matrix d iteratively from right by multiplying last element in 1st row with (1-int*dt) to generate 2nd last element. The replacement continues till I reach the 1st ...
4
votes
2answers
130 views

Coarse-graining in numerical integrations

I have been working recently in a coarse-graining problem I found when using NIntegrate: I am trying to evaluate the function $$f(a)=\int_0^{\infty}x\,e^{-(a^2+b^2)x^2}\text{d}x$$ numerically as a ...
0
votes
0answers
55 views

How to replace a part of array based on certain rules which involves usage of other array

I am trying to replace outermost column of array "fd" in below code. fd is matrix of dimension (nas1,nts) which is initially filled with 1. I want to replace outermost column of fd with result of Max ...
2
votes
0answers
66 views

What is the difference between GenerateDocument and TemplateApply[NotebookTemplate[

Abstract GenerateDocument[ _NotebookObject ] seems to do the same what TemplateApply[ NotebookTemplate @ _NotebookObject ] ...
4
votes
0answers
86 views

Using an external Pattern breaks Format

I noted while writing this answer that using an external Pattern on Format doesn't work: ...
1
vote
2answers
178 views

How can I create function which contains an ODE system and its numeric solution?

I have created a function like the following, which contains an ODE system. And I want to know the effect of different parameters. ...
0
votes
2answers
216 views

FindShortestTour to solve Traveling Salesman Problem

I'm trying to write my own code to find the shortest route but I'm lost on how or where to start. Does anyone have any idea how the FindShortestTour function works? What type of algorithm or structure ...
9
votes
1answer
309 views

solve ODE with divergencies

The solutions of the second order differential equation $$\frac{1}{\eta}\frac{d}{d\eta}\left(\eta \frac{df}{d\eta}\right)+\left(1-\frac{s^2}{\eta^2}\right)f-f^3=0$$ is shown in Fig. 5.2 below, for ...
15
votes
6answers
1k views

Will Version 9 functions all work in Version 10?

Having developed a substantial code base in Mathematica 9, leads me to ask these important questions prior to downloading and installing Mathematica 10. Will any Mathematica functions from the ...
22
votes
3answers
845 views

DeleteDuplicatesBy is not performing as I'd hoped. Am I missing something?

Déjà vu: a new-in-v10 function should provide a better solution to an old problem, but my enthusiasm is curbed when I run timings. This time the function is ...
1
vote
1answer
75 views

How to Reap data from a ScheduledTask?

Here is an amusing little function mapped over a range just to iterate it. It ignores its argument and works entirely by side-effecting a global variable: ...
3
votes
1answer
164 views

How do I create an array by applying a function to the index of each element?

I am looking for something like matrix(m, n, f), but for Mathematica rather than MuPAD, and for arrays rather than matrices. That is, I'm looking for a(n ...
2
votes
0answers
54 views
43
votes
2answers
4k views

What is so special about Prime?

When we try to evaluate Prime on big numbers (e.g. 10^13) we encounter the following issue : ...
0
votes
1answer
88 views

Can we say that “all functions in Mathematica are some kind of pattern-matching-and-replacement procedures”? [duplicate]

Currently I am studying Mathematica programming, and when I study pattern matching and replacement, I find it is quite similar to functions. So can we say "all functions in Mathematica are some kind ...
1
vote
0answers
89 views

How can I use L.Shifrin s code formatter package better

in the document of HoldAllComplete, it says: Evaluate cannot be used to override HoldAllComplete.. for example, when I'm ...
0
votes
1answer
42 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 ...
22
votes
1answer
470 views

Why does list assignment with a packed array result in unpacked values?

Bug introduced in 5.2 or earlier and fixed in 10.1.0 This is another question on the design choices in Mathematica. I understand that without direct reply from the developers it may not be ...
1
vote
1answer
104 views

How to fill a Marshal buffer with whitespace using NETLink

Further to Todd Gayley's answer on string handling in a DLL function, I have the following code: ...
3
votes
1answer
57 views

LineScaledCoordinate problem for exact coordinates

Edit: Confirmed bug. CASE:2326540. Still the case in V 10.1. Solution: Wait and use N meanwhile. I've faced this problem ...
0
votes
1answer
75 views
0
votes
1answer
74 views

Calculating functions of sounds

I've seen that it is possible to create a sound from functions: Sound[{Play[Sin[1000 t (1 + t^2)], {t, 0, .2}], Play[Sin[500 t (1 + t^3)], {t, 0, .5}]}] Is is ...
6
votes
2answers
72 views

Maximise output issue

When I execute the following command, I get a numerical output as follows: ...
10
votes
4answers
4k views

How can I differentiate Numerically?

Mathematica has two ways to integrate: Integrate and NIntegrate. But what about D? ...
1
vote
3answers
160 views

How to calculate time period?

I have the starting and ending dates and times. And I need to calculate the night time in this period (from 10 pm (22) to 6 am (6)). Example: starting date and time is {2015, 1, 4, 3, 10} ending date ...
6
votes
4answers
261 views

What is shorthand way of Reap list that may be empty because of zero Sow

Sometimes because of conditionals, you cannot guarantee that Sow will be called at least once. Reap[Sow[1]][[2,1]] results in ...