## Search found 22 matches

- Sun Nov 04, 2012 11:35 am UTC
- Forum: Mathematics
- Topic: Finding the derivative of a matrix equation
- Replies:
**4** - Views:
**1336**

### Re: Finding the derivative of a matrix equation

I'm sorry, I gave an incorrect example, it has been fixed

- Sun Nov 04, 2012 2:39 am UTC
- Forum: Mathematics
- Topic: Finding the derivative of a matrix equation
- Replies:
**4** - Views:
**1336**

### Re: Finding the derivative of a matrix equation

Let A=[a_lm] be the matrix Xf(X). Then Tg(Xf(X)) is a vector valued function, from R^(n^2) to R^n taking X=[x_lm] to [Σg(a_1m),...,Σg(a_nm)] where sums are from m=1 to n. But Tg(Xf(X)) ends up being a scalar, f(X) is n x 1, X is n x n, g does not alter the dimensions and T is 1 x n giving us, Or di...

- Fri Nov 02, 2012 10:47 pm UTC
- Forum: Mathematics
- Topic: Finding the derivative of a matrix equation
- Replies:
**4** - Views:
**1336**

### Finding the derivative of a matrix equation

I have an expression and need to find the derivative but I am not sure of my results. X is a square matrix with the components x_ij were i denotes row and j denotes column. g(X) is a know function applied componentwise to the matrix x, for example if x=[1 0] and g(X)=sin(X) then g(X)=[sin(1), sin(0)...

- Sat Mar 17, 2012 11:44 am UTC
- Forum: Mathematics
- Topic: Simple graph theory terminology question
- Replies:
**9** - Views:
**1359**

### Re: Simple graph theory terminology question

Ok, thanks for the help people

- Fri Mar 16, 2012 5:47 pm UTC
- Forum: Mathematics
- Topic: Simple graph theory terminology question
- Replies:
**9** - Views:
**1359**

### Re: Simple graph theory terminology question

Ah, I am sorry I should have stated it as a simple path. I will now edit my original post to reflect this.

- Fri Mar 16, 2012 4:55 pm UTC
- Forum: Mathematics
- Topic: Simple graph theory terminology question
- Replies:
**9** - Views:
**1359**

### Re: Simple graph theory terminology question

With length I mean that with each edge having a given distance. the length of a path is the sum of the edges contained in the path. As per the normal definition of the shortest path problem

- Fri Mar 16, 2012 1:31 pm UTC
- Forum: Mathematics
- Topic: Simple graph theory terminology question
- Replies:
**9** - Views:
**1359**

### Simple graph theory terminology question

What is a directed graph called if it has the property that all simple paths from some node n1 to a node n2 have the same length? (in this case length is defined as weights given to each edge in the usual manner of the shortest path problem)

Edit: added the requirement of the graph being simple

Edit: added the requirement of the graph being simple

- Fri Mar 09, 2012 4:45 pm UTC
- Forum: Mathematics
- Topic: Probability paradox?
- Replies:
**40** - Views:
**5961**

### Re: Probability paradox?

What range does the random number generator operate in?

if it takes a random number in (0, inf) then it will always generate inf. So just find the upper bound on the generator and you get the number of possible answers.

if it takes a random number in (0, inf) then it will always generate inf. So just find the upper bound on the generator and you get the number of possible answers.

- Fri Mar 09, 2012 4:36 pm UTC
- Forum: Mathematics
- Topic: [linear optimization] Is there a transformation such that
- Replies:
**0** - Views:
**730**

### [linear optimization] Is there a transformation such that

In linear optimization each basic solution (not necessarily feasible) in the primal problem is equivalent to a basic solution in the dual problem. Is there a transformation from the primal to the dual (or vice versa) such that 1. All basic solutions in the primal are mapped to the corresponding basi...

- Thu Mar 08, 2012 12:00 am UTC
- Forum: Mathematics
- Topic: Simple binomial coefficient question
- Replies:
**5** - Views:
**1255**

### Re: Simple binomial coefficient question

Ok, thanks.

Unforunate that there is no more elegant way to write it.

n<=q

n<=p

So I can't use ++$_ suggestion.

Thanks for the help

Unforunate that there is no more elegant way to write it.

n<=q

n<=p

So I can't use ++$_ suggestion.

Thanks for the help

- Tue Mar 06, 2012 3:56 pm UTC
- Forum: Mathematics
- Topic: Simple binomial coefficient question
- Replies:
**5** - Views:
**1255**

### Simple binomial coefficient question

Is it possible to simplify the sum

[imath]\sum_{t=1}^n \begin{pmatrix}

p\\ t \end{pmatrix} \begin{pmatrix}

q\\ t \end{pmatrix}[/imath]

Can't seem to get the math typing to work, so I'll rewrite it to be readable

sum_{t=1}^n (p t)(q t) where (p t) is p choose t.

[imath]\sum_{t=1}^n \begin{pmatrix}

p\\ t \end{pmatrix} \begin{pmatrix}

q\\ t \end{pmatrix}[/imath]

Can't seem to get the math typing to work, so I'll rewrite it to be readable

sum_{t=1}^n (p t)(q t) where (p t) is p choose t.

- Wed Feb 08, 2012 5:15 pm UTC
- Forum: Mathematics
- Topic: Random xkcd comic problem
- Replies:
**11** - Views:
**1969**

### Re: Random xkcd comic problem

Does that really change anything?

The first 200 give you unique comics. Then you have (n-200)/((n-200)-x) for each comic x>=200, from tomtom2357s solution

The first 200 give you unique comics. Then you have (n-200)/((n-200)-x) for each comic x>=200, from tomtom2357s solution

- Thu May 14, 2009 7:38 am UTC
- Forum: Books
- Topic: I need a book recommendation (Renamed : Recom'd me a book)
- Replies:
**327** - Views:
**171935**

### Re: Recommend me a book

Neuropath, its not very funny but quite philosophical, and a wee bit disturbing.

It delves into the human mind and how your mind makes you what you are. Its also quite likely to mess up your head

It delves into the human mind and how your mind makes you what you are. Its also quite likely to mess up your head

- Wed Jan 07, 2009 9:22 am UTC
- Forum: Individual XKCD Comic Threads
- Topic: 0527: "Keynote"
- Replies:
**52** - Views:
**9619**

### Re: "Keynote"

Where did the comic go? I can't seem to find it.

- Sat Apr 19, 2008 10:34 pm UTC
- Forum: Gaming
- Topic: Physics Fluxx
- Replies:
**3** - Views:
**1059**

### Re: Physics Fluxx

btw if anyone is interested I can give you a file using the "magic set editor" with a fluxx template to print this deck as ready to play fluxx cards.

- Fri Apr 11, 2008 11:33 pm UTC
- Forum: Gaming
- Topic: Physics Fluxx
- Replies:
**3** - Views:
**1059**

### Re: Physics Fluxx

Creepers: When you draw a creeper you must immidiately place it on the table in front of you and draw another card. I use creepers for rules that apply only to the player who has them on the table infront of them. Oh and creepers are usually bad for you. They are from zombiefluxx but I'm using them ...

- Fri Apr 11, 2008 10:00 pm UTC
- Forum: Gaming
- Topic: Physics Fluxx
- Replies:
**3** - Views:
**1059**

### Physics Fluxx

I am in the process of designing my own fluxxdeck. The deck is supposed to be added to a regular fluxx deck. Critique is welcome as is any ideas for names (not my strong suite, or rather I'm really bad at it) and any card ideas. Some of these cards I've stolen from the internet, some are my own crea...

- Mon Feb 25, 2008 6:33 pm UTC
- Forum: Gaming
- Topic: Urban dead (GRAAAH!!!)
- Replies:
**444** - Views:
**34481**

### Re: Urban dead (GRAAAH!!!)

I haven't played this game for some time.

anyone want an overexperienced account?

anyone want an overexperienced account?

- Fri Feb 22, 2008 5:43 pm UTC
- Forum: Gaming
- Topic: Premade D&D Campaigns/settings/adventures
- Replies:
**7** - Views:
**7955**

### Re: Premade D&D Campaigns/settings/adventures

The only premade adventure I have played the party screwed up badly. We were playing the "Bastion Of Broken Souls" Example: Demogorgon is hunting a member of the party. Half the party decides that it would be a good idea to join up with and help him. That changed the plot somewhat, not to ...

- Fri Feb 22, 2008 6:20 am UTC
- Forum: Individual XKCD Comic Threads
- Topic: 0387: "Advanced Technology"
- Replies:
**105** - Views:
**24870**

### Re: "Advanced Technology" Discussion

Unnervingly accurate comic this time.

- Fri Feb 22, 2008 6:19 am UTC
- Forum: Books
- Topic: Recomend me some Sci-Fi !
- Replies:
**107** - Views:
**18874**

### Re: Recomend me some Sci-Fi !

Dune is a must read.

Ender is advisable as well.

Ender is advisable as well.

- Wed Dec 26, 2007 7:35 pm UTC
- Forum: General
- Topic: INTRO THREAD THE THIRD
- Replies:
**10854** - Views:
**1924502**

### Re: POST HERE FIRST - INTRO THREAD THE THIRD

My name is Henrik, I live in Stockholm. Currently studying physics at R.I.O.T (Royal Institute of Technology).

Just love the comic, have been reading some on the forums so I might as well register. I have been following the comic for half a year or so now. A friend sent the link my way.

Just love the comic, have been reading some on the forums so I might as well register. I have been following the comic for half a year or so now. A friend sent the link my way.