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

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10
votes
1answer
340 views

Why does the documentation call functions “pure”?

Clearly, functions in mathematica are not pure functions according to the definition on Wikipedia (no side effects - basically implementabe with table lookups): ...
0
votes
0answers
45 views

Should this be equal to Gamma function or not?

I define the following function: Nat2[s_] := InverseFourierTransform[FourierTransform[1/t, t, w] (-I w)^(s - 1), w, x]/Cos[Pi (s - 1)] /. x -> 1 I expected ...
1
vote
1answer
140 views

handling division by zeros and line equations

today I was writing a code which takes some line equation and a circle equation,finds intersection points that are on $II$ and $III$ quadrants,draw a tangent line to circle from that point and then ...
1
vote
1answer
58 views

Multiway Systems Rules List Management

I'm working with a multiway system and I have a number of different mutation rule lists. I need an efficient way of managing which rule lists I apply. Here is the basic multiway system code that I'm ...
1
vote
1answer
104 views

Plotting a function in {X(Y),Y} space

The code below generates some data and defines a function f[x,cb]:=NMaximize[expr,x] that upon being evaluated returns: {function value at max $x$,the function maximizing $x$}. ...
14
votes
1answer
275 views

Why do big-O terms disappear in definite integrals since Mathematica 9?

In Mathematica 8, when I computed the following input: Integrate[Series[Cos[x], {x, 0, 2}], {x, 0, a}] Mathematica returned an expression that had a O[a^4] in ...
7
votes
2answers
208 views

How to redefine the type of multiplication in Det

I would like to redefine the type of multiplication that is used in Det (calculates the determinant). Instead of the standard multiplication I would like to use a custom function Fun[a,b] (which takes ...
1
vote
1answer
85 views

User defined functions and decimal places displayed

I have a couple of complicated user-defined functions, one which calls the other, and I wish to control the number of decimal places displayed when I call the "mother" function. I have tried the ...
1
vote
1answer
79 views

In which version was this Extract syntax introduced?

In Mathematica 10.0.1 this works: Extract[{a, b, c, d, e}, {{{1, 3}}, {{5, 4}}, {{2}}}] {{a, c}, {e, d}, {b}} In ...
3
votes
0answers
259 views

Distance Time Warp (DTW) function implementation in mathematica

The DTW (Distance time warp) is given here http://en.wikipedia.org/wiki/Dynamic_time_warping There is an implementation of DTW in R as well as MATLAB. However i am unable to find something for DTW in ...
5
votes
1answer
118 views

FlipView can't handle CurrentValue[“MouseOver”]. Kernel crash

Is this code crashing your Mathematica session? (it can so look out :P) ...
2
votes
2answers
189 views

Returning the 3-dimensional vector from a skew symmetric matrix

I'm trying to write a function that takes in a skew symmetric matrix and returns the corresponding vector. When I write the following code, it works when I leave it as variables, but it does not work ...
4
votes
2answers
149 views

Can't figure out how to apply these functions repeatedly

I have the following problem, and even though I've tried Fold & Inner, Sow & Reap, et al. I can't figure out the clean way to do this. Here's the problem. I have a list that starts as ...
1
vote
1answer
222 views

C compiler error: the no library could be generated error

I have windows 8, Mathematica 9, and I've just installed Microsoft Visual Studio 2013 with update 3. I'm try to run Compile with the option ...
15
votes
6answers
788 views

How can I evaluate only a single step of a recursive function?

Let's say have a simple recursive function for the Fibonacci sequence f[0] := 1 f[1] := 1 f[n_] := f[n - 1] + f[n - 2] but I want to see how it will expand in a ...
7
votes
2answers
598 views

How to create a function like in Python

I want to call a function that would perform a function rather than assigning an expression to them. I.e. ...
0
votes
2answers
76 views

How do I get a Do function to create a list?

I have a Do function which gives me a column of expressions. How can I get the Do function to give me these expressions in a list. i.e The do function gives me this: a b c d I would like it do give ...
0
votes
2answers
2k views

Problem in downloading “ToMatLab” package [duplicate]

Iam trying to download "ToMatLab" Package from http://library.wolfram.com/infocenter/MathSource/577/ but it is showing me an error message by showing a big question mark and "File could not be ...
0
votes
1answer
98 views

Functions in functions

I have three functions f(x,y) , g(t) , and h(t) and somehow I have to find (d/dt)f(g(t),h(t)) where t = 0. How would I go about writing this in Mathematica? In this equation g(t) is taking place of x ...
0
votes
2answers
184 views

Time value of Money Functions combined

I am trying to combine multiple functions into one. I have defined following functions: (PV refers to Present value, FV refers to Future value, i or IPER refers to interest per period, pmt refers to ...
2
votes
3answers
372 views

Extracting coefficients from a power series

I have a function defined explicitly as a power series: $$\sum_{n=0}^\infty{T_n}\frac{x^n}{n!}=\frac{\frac{x^3}{3!}}{e^x-1-x-\frac{x^2}{2!}}$$ and I would like to extract the coefficients $T_k$ as ...
0
votes
2answers
137 views

Collapsing summation

I am trying to write a command to collapse the sum of terms into an expression with summation. Something like ...
11
votes
3answers
247 views

How to deal with the condition $u_i=u_{i+1}$ in B-Spline basis function?

The defintion of B-Spline basis function as shown below: Let $\vec{U}=\{u_0,u_1,\ldots,u_m\}$ a nondecreasing sequence of real numbers,i.e, $u_i\leq u_{i+1}\quad i=0,1,2\ldots m-1$ $$N_{i,0}(u)= ...
4
votes
2answers
316 views

Cleaning up InverseLaplaceTransforms in Mathematica

I am attempting to use Mathematica to model an electrical circuit in the s domain. The circuit contains capacitances and and inductances. I've written a series of equations using Kirchoff's laws to ...
3
votes
2answers
88 views

Conditional replace of a column

Im trying to replace the value in the Nth column of a list if a condition is true, returning the modified list. I've tried modifying the answer from 61219 and been through most of related questions ...
1
vote
2answers
141 views

function of derivative of a function

I know a similar question is answered somewhere, but it doesn't work for my case for some reason. I have the following problem in Mathematica. I want to compute f[h[x]]= x^2 + D[h[x],x]. Here, h[x] ...
2
votes
2answers
360 views

How to explain NDSolve that functions must be positive only?

I have a simple system of differential equations to solve but both functions should be positive: x[t] > 0 and y[t] > 0 for all t. I was not able to explain NDSolve this fact so it goes x[t] < 0 ...
0
votes
1answer
37 views

Rigging a function to output a distinct value every nth call

There's some fixed script I am unable to alter (keeping things simple: Table[f[i], {i, 1, 10}]), , however, I can alter a function that the script calls (again, ...
0
votes
1answer
42 views

Trouble definining a function to use only certain heads

I'm trying to write a function that accepts only a particular Head (for example, prints only Symbols) using pattern matching. However, the following code has me a bit of confused. ...
5
votes
4answers
940 views

Generate random points in a region with higher probability in a sub-region

I am trying to generate random samples of points in the unit square in such a way that points inside a given circle are twice as likely to be selected as points outside of that circle. I tried to ...
4
votes
4answers
121 views

CoefficientRules for negative powers

CoefficientRules acts like the following. ...
4
votes
1answer
306 views
0
votes
0answers
42 views

How can I mix // with a function of two arguments? [duplicate]

I often find myself using // when playing around with expressions, but it is always cumbersome to have to switch to the full notation just to apply a function of ...
1
vote
2answers
92 views

How to define a function that counts the exponents

I want to define a function $F$ described as follows: The input of $F$ is a polynomial such as m*u*x^4*y + n*v*x^2*y^3 where $m$ and $n$ are constants, and ...
1
vote
0answers
33 views

Analog of GeneratingFunction for Newton series [duplicate]

GeneratingFunction gives the generating function for Maclauren series. I wonder if there a similar function for Newton series. If $$g(x)=\sum_{k=0}^{\infty}\frac{x^k}{k!}f(k)$$ Then g(x) is ...
23
votes
3answers
1k views

Visualisation of a recursive function

Is there a way to nicely visualize recursive functions? (diagrams/plots) More specifically I'm looking for a way to make contrast (visually) between e.g. the cosine function which if continuously ...
8
votes
2answers
211 views

Is there a way to revert to the built-in function after overwritting it using Unprotect

When using Unprotect, we can overwrite a functions definition: Unprotect[Sqrt] Sqrt[x_]="blahblah" Protect[Sqrt] Once this is done, can we revert to the built-in ...
14
votes
3answers
2k views

Fitting ellipse to 5 given points on the plane

Five points are required to define a unique ellipse. An ellipse has five degrees of freedom: the $x$ and $y$ coordinates of each focus, and the sum of the distance from each focus to a point on the ...
5
votes
5answers
268 views

Replacing columns of a matrix with zeros

I am to create a function that replaces columns 'm' through till 'n' with zeros. Here is what I have so far: ...
3
votes
1answer
154 views

How do I format Compile[] correctly?

My Mathematica skill is still rusty, so kindly bear with me. I'm having problem formatting expression to compile the function correctly: $\sum _{g=1}^G \sum ...
2
votes
3answers
159 views

Function to Expand exponentials

Is there a function similar to PowerExpand which expand exponentials? This would, for example, take Exp[5(a + b)] and ...
7
votes
5answers
2k views

Find function inverse

I'm trying to find the inverse of a function: (30*x^2 (1 - x)^2) (* where 0<x<1 *) I tried all the following options: 1. ...
7
votes
2answers
565 views

Modifying parameters: Set::setps in the part assignment is not a symbol [duplicate]

Ok, this will probably be a silly question, but I can't get my head around it. I'm making a simple module that, given a list and two integers, will swap the position of the elements in the ...
3
votes
1answer
107 views

JordanDecomposition in Mathematica

I'm trying to find the Jordan Decomposition in Mathematica for $$ A=\left( \begin{matrix} 2& -5& 8&-12\\ 1& -2& 4&-8\\ 0&0&2&-5\\ 0&0&1&-2 \end{matrix} ...
3
votes
1answer
227 views

StreamPlot in Mathematica

A $2\times 2$ linear ODE system can be visualized by StreamPlot in Mathematica. For example: ...
3
votes
1answer
122 views

Ted's explanation for the 3rd argument of ListCorrelate doesn't apply to the {1, -1} case?

I was reading Ted Ersek's explanation for the usage of ListCorrelate(.nb version can be found here) and noticed something confusing. It's the third example of ...
14
votes
2answers
1k views

Extracting the function from InterpolatingFunction object

I've used Interpolation[] to generate an InterpolatingFunction object from a list of integers. ...
40
votes
2answers
1k views

Why is the new PositionIndex horribly slow?

This issue has largely been mitigated in 10.0.1. New timings for the final test below are: ...
4
votes
0answers
242 views

Strange behaviour of MMA in derivatives of some standard functions

There are some peculiar things to be discovered in derivatives of some standard functions in MMA: Strange behaviour Example 1: Abs We have ...