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

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6
votes
5answers
933 views

Prevent Part[] from trying to extract parts of symbolic expressions

If you have a list, e.g. {1, 2, 3} then you can extract the $k$th part using Part (...
1
vote
1answer
97 views

Using Map in a function definition

I want to calculate the hessian of a matrix. So each element gets replaced by a 2 by 2 matrix. ...
0
votes
0answers
52 views

Is it possible to calculate with declarations only?

simple Example: maximize $u(x), x$ solution would show constraints: $\frac{\partial u(x)}{\partial x} = 0$ $\frac{\partial^2 u(x)}{\partial x} < 0$ etc... or do I always have to explicitly ...
11
votes
4answers
671 views

Plot the minimum of a list of functions

This is my first question on any stack-exchange site and I'm also very new to using Mathematica software so please excuse/correct me if I mess up. I would like to take a list of functions of a single ...
0
votes
0answers
85 views

How to be faster at making a frequency list of increasing steps

I want to find propabilities of having a sequence in a list, by using frequencies. The case is that you will bet on an increase when the last event had an increased and bet on derease when the last ...
0
votes
0answers
101 views

Timing: how make a program to work faster using built in functions and tables

I want to improve my code to make it working faster even for very large numbers. ...
1
vote
1answer
86 views

Bug in NDSolve (Mathematica 9.0.1)? [duplicate]

The following code performs many times the same identical operation, but the time it takes increases systematically. This seems to be a problem of Mathematica 9.0.1 and above. Mathematica 9.0.0 does ...
0
votes
1answer
65 views

Combining functions - is this a case for Piecewise?

I have a function $Eb1$ which was the subject of a question I asked recently - you can see it here on stack exchange. Now, in that example it's specified between a boundary $r_n$ and $r_o$ where $r_o ...
0
votes
1answer
77 views

How can I represent this automorphism of Q(i,a)?

Let $a$ represent some real irrational number. I am trying to perform computations with an automorphism $f:\mathbb{Q}(i,a)\to\mathbb{Q}(i,a)$ which fixes $\mathbb{Q}(i)$ pointwise and maps $a$ to $i ...
0
votes
1answer
90 views

How to track row swap in Gaussian elimination?

How do I track which rows were swapped in the Gaussian elimination using RowReduce? I am doing metabolic control analysis on a mathematical of the energy metabolism I have in Mathematica. I need to ...
8
votes
3answers
737 views

Why are functions called first-class objects in Mathematica?

I've heard lots of people say a function is a first-class object in Mathematica. "Everything is an expression, including function." "There is no distinction between functions and data." Having read ...
4
votes
3answers
740 views

Simplify function notation

I have some calculations with arbitrary functions. In the output, Mathematica always shows the functions with its arguments. I would like to tidy the notation a bit, by hiding the arguments in the ...
10
votes
8answers
1k views

Finding maximum or minimum of implicit functions

is there any built in function that can be used to find maximum or minimum of implicit functions? For example, if we have the equation $$x^2 + y^2 = (2 x^2 + 2 y^2 - x)^2,$$ then we can visualize the ...
11
votes
1answer
321 views

Overloading second argument of CountryData

For convenience I'm trying to add an extra property to CountryData ...
10
votes
4answers
1k views

How to find the domain and range of an implicit function?

For example, we have this curve: $$ x^2 + y^2 = 1 $$ Is there a function in Mathematica for finding out that the ranges for $x$ and $y$ are both [-1, 1]? What ...
2
votes
2answers
97 views

Funny behavior of Ellipsoid function

From its description I thought that the normalizations of the directions d_i of the semi-axes did not matter when using the ...
-1
votes
3answers
128 views

Creating Do loop that cycles back to earlier values

I need to create a Do loop that distributes letters in a list of lists. I also need to be able to cycle back through to the beginning of the list. For example, I ...
2
votes
0answers
102 views

Which functions automatically generate new functions?

In his video http://www.wolfram.com/broadcast/video.php?channel=362&video=1643, Wolfram gives the following example: the output from ...
0
votes
1answer
119 views

Laplacian in D Dimensions

Is it possible to compute $\Delta F=\nabla^2 F$ for $F=F(x^1,x^2,…,x^D)$ with $D$ finite? I seem to be only able to specify spherical coorindates, for example, if I want to leave standard ...
13
votes
4answers
527 views

How to make a function with its own options as well as passing options to other functions [duplicate]

I have a function with many of its own options, but I would also like to pass options to subfunctions using the FilterRules function. Here's a simple example: ...
0
votes
1answer
107 views

Cannot solve equation

I just started using mathematica and I'm facing a problem that I just can't solve. I want to solve the following equation: Code: ...
1
vote
1answer
103 views

How can I define a function that takes a list of reals?

I'm trying to define a function f which takes a list of reals. My purpose is to build a function which I can give a list of reals, integers or strings and have it ...
0
votes
2answers
178 views

Defining a function as a sum of several Gaussians

I have a function that is a summation of several Gaussians. Working with a 1D Gaussian here, there are 3 variables for each Gaussian: A, ...
2
votes
3answers
448 views

Tracking iterations of a function

I'm learning MMA with Wagner's book. On page 41, he uses this to display the iterative steps of a FindRoot. However, I can't seem to replicate this (code at end), perhaps due to the difference in MMA ...
6
votes
1answer
290 views
0
votes
3answers
94 views

Create polynomials from Series

This question actually doesn't have quite a lot to do with the Series function, but I don't know how to describe my problem. So here's the thing. I'm trying to ...
2
votes
1answer
240 views

Define function that counts recursive fibonacci

If I write count=0; fib[0]:=(count=count+1; 0); fib[1]:=(count=count+1; 1); fib[n_] := (count = count+1; fib[n-2] + fib[n-1]); Then I can ...
5
votes
4answers
847 views

How to completely delete the head of a function expression

Is there any way to completely remove the head of an expression function? For example, how would I remove the head Cos from ...
1
vote
0answers
111 views

Expression for evaluating multiple functions?

I am constructing 3D data points for a plot and corresponding to specific conditions "manually". I define the values of five parameters [these I always have to define myself]. From those, I evaluate ...
4
votes
3answers
260 views

Counting number of inversions

Is there an inbuilt method to find the number of inversions in a set of numbers? I found Inversions in Combinatorica but when I ...
0
votes
1answer
71 views

Switching the ordinate and abscissa causes problem in `ParametricPlot`

I have a function that plots properly in PolarPlot, but I'd like to plot it in ParametricPlot and then switch the y and x ...
0
votes
1answer
181 views

Getting “Null” output from package?

I have a script written to test a package as follows: ...
0
votes
1answer
113 views

Is there a way to make the MemberQ function apply to a list?

Is there any way to ask a boolean question if the elements of the list {2,5} are in the list {1,2,3,4,5}?
0
votes
1answer
68 views

How I can define a new function as a function argument?

I need to pass a function with t as independent variable as a function parameter and want to create a new function of the same through this provided the argument of another function. Here is my code. ...
2
votes
3answers
309 views

find connectivity

Imagine a chain of 20 rings, labeled by 1-20 sequentially. We want to make random size sets of numbers randomly chosen from these 1-20 rings. No duplicate numbers are allowed. Example of a set: ...
0
votes
2answers
1k views

How to pass a list as function argument?

I have the following function lFreqPhylo[a_, Q_, b_, p_] := Sum[Log[freqFunction[r[[p]][[i]], L[[p]][[i]], a, Q, b, {i, 1, nbranches[[p]]}]; The objects L, r ...
1
vote
0answers
96 views

How to find matrix exponential using RootSum?

From what I've been able to deduce, Mathematica uses a root sum scheme to determine the exponential of a matrix. Can someone please explain to me the theory behind this? I've searched, but have had no ...
2
votes
2answers
252 views

Restarting an Animate animation after variable in Manipulate changes

I've been trying to restart an animation after variables change from Manipulate PopUpMenus. My animation takes the form: ...
7
votes
0answers
163 views

Finding hidden treasure (aka finding undocumented functions) [duplicate]

I was searching for a way to determine if a point is within a polygon and stumbled upon rm -rf's answer. (actually, I really wanted to find a point within a ...
1
vote
1answer
84 views

Apply function to output of previous function

I am trying to write a function that takes 3 tuples. Each tuple contains two lists which are first divided. This results in 3 lists. Then I want to take the Mean of all the columns. I can do this ...
1
vote
1answer
66 views

ToExpression and Fortran notation

ToExpression["9.0E-03"] interprets String as 9*e - 3 instead of what I am expecting ...
0
votes
1answer
370 views

Discrete peaks to curve via Voigt summation

I have two data sets. One is an experimental recording of an absorption spectrum, composed of regularly spaced (wavenumber, intensity) coordinates with a fine wavenumber resolution, thus making ...
2
votes
2answers
139 views

Graphical solution of a a two-variable system containing an equation and an inequality

I'm currently studying atmospheric-gravity waves and their dispersion relations. I want to have look at values of $(x,y)$ that solve the following system : \begin{equation}\label{}(1) \left\{ ...
0
votes
1answer
93 views

Inverse functions - how are they calculated?

Mathematica is able to calculate InverseFunction[LogIntegral] and InverseFunction[RiemannR] (and many other inverse functions). ...
1
vote
0answers
83 views

Find eigenvalues without filling the matrix

Is it possible to find eigenvalues of a matrix without filling it? The matrix elements are given by a known function f[p1,p2]. This is relevant for a matrix too ...
1
vote
1answer
68 views

Get subgraphs: communities of graph g

I have a graph g. I want a set of graphs c which holds the community subgraphs of g. I ...
2
votes
1answer
141 views

Why evaluation doesn't fail if arguments are invalid? [duplicate]

Sorry for a noob question, but this is something that I wonder about each time I work with Mathematica. Coming from standard programming languages (Python and Java), I expect my functions to fail ...
1
vote
1answer
122 views

How to study the sign of an expression including a function, with conditions on the function?

I'm trying to study the sign of an expression, having information on some of my parameters. I don't know how to code these conditions. For example, I want to know when this expression: ...
1
vote
1answer
91 views

Sort lists of vertices {indegrees, outdegrees} by indegree

in = VertexInDegree[F]; out = VertexOutDegree[F]; I want both in and out to be ordered by in. Example: graph has nodes a,b,c with indegrees 1,2,0 and outdegrees ...