## schematics-development — Discussion of Schematics project and code development

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 [Schematics-development] Schemathics: Documentation of random variables From: - 2003-04-30 18:38:04 ```Noel Welsh: > Ewwww that code is old. :-) > Anyway, here's the straight dope as I remember it: > make-discrete-random-variable creates a random > variable that generates values from a finite set > (maybe it ain't a random variable then - I'm not > sure on the terminology). So > > (make-discrete-random-variable > '((a . 0.1) (b . 0.6) (c . 0.3))) > returns a rv that generates values from the set > {'a, 'b, 'c} with the probabilities given above. > The only export is make-discrete-random-variable Ok, the argument is simply the distribution function represented as an association list. > make-graph-random-variable makes a discrete random > variable where the output is determined by > following a graph of discrete random variables (so > its really a markov chain). You can either sample > from graph or trace the path through the graph. I > think the concepts are a bit muddled up here. Do you know a reference to a definition? I don't think graphs of random variables was covered in the probality course I had [although I vaguely remember calculating eigenvalues for some Markov matrices]. > constant-process is a "random" variable that > always returns the same value. Ok. > Dirac delta function I guess. The Dirac delta function is "infinity" in one point and zero elsewhere. Well, actually it's not a function at all, but a so called distributiun [the set of distributions is a extension of the space of functions], but that doesn't bother physists. (I can't blame Dirac, the theory of distributions was initiated by his work, if I remember correctly]. > tree-process....hmmm....I think this was a hack I > created to test a decision tree algorithm. I > think it generates data from a noisy decision > tree. I don't think its generally useful. Ok. > BTW, info.txt is really nice. Thanks - speak up if you find spelling errors and the like (english is not my native tongue). After writing the documentation, I accidently fell over "SRFI 27: Sources of Random Bits", which is very well written. The basic generator of random bits in SRFI 27 is better (but slower) than the one from Numerical Recipes. I think I'll port it this summer, and then use it to rewrite some of the functions. ; -- Jens Axel Søgaard -- Jens Axel Søgaard ```
 [Schematics-development] Re: Schemathics: Documentation of random variables. From: Noel Welsh - 2003-04-30 14:02:45 ```Ewwww that code is old. Anyway, here's the straight dope as I remember it: make-discrete-random-variable creates a random variable that generates values from a finite set (maybe it ain't a random variable then - I'm not sure on the terminology). So (make-discrete-random-variable '((a . 0.1) (b . 0.6) (c . 0.3))) returns a rv that generates values from the set {'a, 'b, 'c} with the probabilities given above. The only export is make-discrete-random-variable make-graph-random-variable makes a discrete random variable where the output is determined by following a graph of discrete random variables (so its really a markov chain). You can either sample from graph or trace the path through the graph. I think the concepts are a bit muddled up here. constant-process is a "random" variable that always returns the same value. Dirac delta function I guess. tree-process....hmmm....I think this was a hack I created to test a decision tree algorithm. I think it generates data from a noisy decision tree. I don't think its generally useful. BTW, info.txt is really nice. HTH, Noel ===== Email: noelwelsh yahoo com Jabber: noelw jabber org __________________________________ Do you Yahoo!? The New Yahoo! Search - Faster. Easier. Bingo. http://search.yahoo.com ```

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