dwf

"""
A demonstration of how to deal with object-specific random number
generator states. One application is if you want two objects to
work with the same pseudorandom sequence but don't particularly
want to generate them in advance, or to replicate results after
serializing and de-serializing an object.

By David Warde-Farley, dwf at cs.toronto.edu, January 2010.
Released under BSD license.
"""

dwf

import numpy as np

def sample_pf_ball(p,b):
    """
    Samples N binary variables using the product form distribution given in
    the vector b (of length N), where b[n] is the probability that s[n]=1.
    However, only K variables may on at a time, where K is the length of
    vector b minus 1, and b[k] is a distribution that biases the number of
    variables set to 1.
    %

dwf

#!/usr/bin/env python
"""
Draws Hinton diagrams using matplotlib ( http://matplotlib.sf.net/ ).
Hinton diagrams are a handy way of visualizing weight matrices, using
colour to denote sign and area to denote magnitude.

By David Warde-Farley -- user AT cs dot toronto dot edu (user = dwf)
  with thanks to Geoffrey Hinton for providing the MATLAB code off of 
  which this is modeled.

dwf

#!/usr/bin/env python
"""
NumPy implementation of the classic 'four regions' benchmark.
By David Warde-Farley -- user AT cs dot toronto dot edu (user = dwf)

Redistributable under the terms of the 3-clause BSD license 
(see http://www.opensource.org/licenses/bsd-license.php for details)
"""

import numpy as np

dwf

"""
tfd.py -- Scrapes a certain set of comics' websites, and spits
          out home-grown RSS feeds for them. 

This is pretty useless now that all of the Sharing Machine comics 
provide RSS feeds, but might serve as an okay example of old-school
screen scraping and XML generation in Python. I hear the cool kids 
use BeautifulSoup (for scraping) and lxml (for XML generation) 
nowadays.

dwf

"""
Simple script I whipped up to dump MSN Messenger logs in XML to a readable 
plaintext format. It's not very robust, nor am I sure which versions of MSN
Messenger it's compatible or incompatible with; I just had a specific 
conversation I wanted to read, and this was the vehicle to that end.

By David Warde-Farley -- user AT cs dot toronto dot edu (user = dwf)
 
Redistributable under the terms of the 3-clause BSD license 
(see http://www.opensource.org/licenses/bsd-license.php for details)

dwf

function bestclass = knn(train_data, labels, example, k);
%kNN-- do k-nearest neighbours classification
%
%  BESTCLASS = knn(TRAIN_DATA, LABELS, EXAMPLE, K)
%
% Takes TRAIN_DATA, a D x N matrix containing N training examples of dimension
% D; LABELS, an N-vector of the (positive integer) classes assigned to each
% column of TRAIN_DATA; EXAMPLE, a D-vector consisting of the example we
% are trying to classify; and K, the number of neighbours to use in
% classifying.

dwf

;A bunch of increasingly complex Scheme procedures I wrote while
;learning Scheme.
;
; By David Warde-Farley -- user AT cs dot toronto dot edu (user = dwf)
; Redistributable under the terms of the 3-clause BSD license 
; (see http://www.opensource.org/licenses/bsd-license.php for details)

;Increment a value and return it.

(define inc

dwf

/* Scanner that reads in a Portable Graymap (PGM) file.
 * 
 * By David Warde-Farley -- user AT cs dot toronto dot edu (user = dwf)
 * Redistributable under the terms of the 3-clause BSD license 
 * (see http://www.opensource.org/licenses/bsd-license.php for details)
 */


    enum { PRE_START, PARSE_START, GOT_X, GOT_Y, GOT_MAX } parserstate 
        = PRE_START;

dwf

import numpy as np
import scipy.special as spec
import scipy.optimize as opt

def negative_beta_likelihood(params, sumlogd, sumlog1md, numpts):
    """
    Negative log likelihood for i.i.d. beta random variables, based
    on the parameters and the sufficient statistics.

        params     -- length-2 array of (log) parameters