RE: [PEAR-DEV] New package proposal: Math_Calculus

Hi Lukasz and Johannes, --- Lukasz Karapuda <luke@thenewline.com> wrote: > > Overall the idea is good. The implementation needs some work. For > example, > > a stable and reliable differentiation package could be use to solve > funding > > the roots of an equations using any of the well-known methods (e.g. > > Newton-Raphson's). > > If you are considering developing a reliable and complete > differentiation package, take a look at http://www.phpmath.com. > Sounds interesting. A more encompasing project than the 'Numeric PHP' (one that I started eons ago, and now have terminated). Most of the code from that is in PEAR now (see the Math_* packages). > It's a > major effort to create a complete mathematical toolkit for PHP (language > based). Went to the site, found not much information. In particular I was expecting to see some downloadable code. I found the autocorrelation, distribution, and linear regression stuff code (some of which can be factored out to other packages, eg. Math_Stats in PEAR). > I am one of the administrators, and currently we are looking at > as many contributors as possible. Perhaps you could join our mailing > list. We currently have implemented Simple Linear Regression, Matrix > Operations and Linear Algebra. I did not see any matrix operations code (see PEAR::Math_Matrix). Also, it would be a good idea to use the PEAR Code Standards, for both the actual PHP code and the code documentation. Also, you might consider creating a package.xml so the classes can be installed using the PEAR installer. Finally, why not consider to create a series of Math_* classes that can be included/integrated in PEAR. Having a team of maintainers that can be grouped under the phpmath.com site would be great, that way the code will be better and the errors/bugs fewer. This can be done in two ways, by adding the packages as they are approved to PEAR's CVS, or by keeping the code in a separate CVS and releasing them via PEAR, or both ;-) > > Best Regards, > > __________________________________________ > Lukasz Karapuda [ lkarap00@mercyhurst.edu ] > Mercyhurst Web Developer > Y! lukaszkarapuda > > > -----Original Message----- > From: Johannes Schlueter [mailto:phpng@schlueters.de] > Sent: Saturday, May 17, 2003 10:03 AM > To: Jesus M. Castagnetto > Cc: pear-dev@lists.php.net > Subject: Re: [PEAR-DEV] New package proposal: Math_Calculus > > On Friday 16 May 2003 23:45, you wrote: > > The class looks OK for simple functions withouth many singular points. > > As it stands now, I would not recommend its inclusion in PEAR: -1 > > Ok. > > > 1) The name of the class: Perhaps you will be better of having 2 or > more > > Math_Numerical_Differentiation, Math_Numerical_Integration, etc. Or > how > > about a Math_Numerical (or Math_NumericalMethod or > Math_NumericalSolution?) > > class that works as facade to the ones implementing the algorithms? > > Math_Numerical looks good, but then we need many method's with it, but > I'll > look how I can implement all useful Numerical Alogrithms with PHP ;-) > > > 2) The implementation of your differentiation function, if you are > handed a > > non-continuous function, then you will be in trouble using the simple > > approach, w/o previously testing for continuity in the interval where > you > > Yes, that's true. The version I posted was the work of very few hours, > just > for solving a problem I had. Therefore it worked. Then I saw there's no > such > thing for PEAR so I wrote some comments to see the reactions, imho it > don't > make sense spending hours of work if nobody wants it ;-) > > > are calculating the derivative. A look at: > > http://lib-www.lanl.gov/numerical/index.html, and in > > particular at: > > http://lib-www.lanl.gov/numerical/bookfpdf/f5-7.pdf, will > > surely help > in > > this respect. Might also need to be careful not to generate an > floating > > point overflow. > > The links look really interesting. All have a closer look over these an > improve my code. > > > 3) The implementation of the Romberg's integration method tries to > minimize > > errors by using iterations of the trapezoidal rule. But for analytical > > functions, you might be better using other approaches. > > Romberg'smethod was the one I've found most implementations for and the > one > I've understood easily ;-) > > > 4) The method that finds point of a function where the derivative is > zero > > is OK, but it is of no use if it is not coupled with one that find the > > extrema (minima and maxima). Also, if might be better named > > findZeroDerivative() instead. Of course you will need to define a > second > > derivative method for the extrema. > > Yes... > > > Overall the idea is good. The implementation needs some work. For > example, > > a stable and reliable differentiation package could be use to solve > funding > > the roots of an equations using any of the well-known methods (e.g. > > Newton-Raphson's). > > > > The URL mentioned above has a lot of great numerical recipes. And as > we > > cannot add GSL to PECL due to licensing conflicts, perhaps > implementing > > them in PHP would be nice. > > If I'm going to implement all of them I'll never be bored again. And if > I'm > still bored I can implement it using BCMath, GMP and PEAR Math_Complex. > ;-) > > johannes > ===== --- Jesus M. Castagnetto (jcastagnetto@yahoo.com) Research: http://metallo.scripps.edu/ Personal: http://www.castagnetto.org/ __________________________________ Do you Yahoo!? The New Yahoo! Search - Faster. Easier. Bingo. http://search.yahoo.com