--Kilian:

Merci pour cette reponse eclaire! Je vous tiens au courant..

Je precise, en fait j'essaie d'ecrire un programme pour faire un regression lineaire:

Il faut ouvrir un fichier de donnees (juste des coordonnees). Comme file.read() pond une string, je dois en extraire les coordonnees que je vais mettre dans une liste.

Ensuite on verra pour la manipulation des donnees..

Coucou, re,

Dans mon programme (ich bin keloss) je tente de separer une liste en deux: avec un sur 2 elements de la premiere liste dans chaque liste fille.

J'ai commence par faire:

def getxnylist(listemere):
       xlist = [n for n in listemere if listemere.index(n) % 2 == 0]
       ylist = [n for n in listemere if listemere.index(n) % 2 != 0]
       return xlist, ylist

def getxlist(firstlist):
        lx = []
        if firstlist:
                lx = [firstlist[0]] + getxlist(firstlist[2:])         
        return lx               

def getylist(firstlist):
        ly = []
        if firstlist:
                ly = [firstlist[1]] + getylist(firstlist[2:])
        return ly
        
def getxnylist(firstlist):
        """Creates two lists. Each list has one out of two elements of the first list.
        
        The first list will represent x-values, the second  y-values."""
        lx = getxlist(firstlist)
        ly = getylist(firstlist)
        return lx, ly    

Bon mais j'ai tout de meme une beta-beta version a vous offrir (pour ces foules silencieuses qui attendaient un programme de regression lineaire..)

import sys

def main():
        """Will calculate a simple linear regression."""
        try:
                filename = raw_input("Which file to import? ")
                f = open(filename, "r")
                try:
                        stringdata = f.read()
                        f.close()
                        okdata = convert(stringdata)
                        xlist, ylist = getxnylist(okdata)
                        T = len(xlist)
                        Ex = sum(xlist)
                        Ey = sum(ylist)
                        Exsq = listsqsum(xlist)
                        Exy = listxysum(okdata)
                        b2 = (T*Exy - Ex*Ey)/(T*Exsq - Ex**2)
                        b1 = (Ey/T) - b2*(Ex/T)
                        print "yt = " + str(b1) + " + (" + str(b2) + ")Xt"                 
                except ValueError:
                        print "Invalid values in there, sorry, only take numbers.."
                        sys.exit()                
        except IOError:
                print "File does not exist!"
                sys.exit()
                
def convert(ustring):
        """Formats input text file into a list of floating numbers.
        
        Admits anything as separators between numbers but '.'. Will take all nu-
        bers in consecutively, ignoring anything in between. Make sure your x-values
        are first."""
        accepted = ('.', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9')
        
        for char in ustring:
                if not char in accepted:
                        ustring = ustring.split(char)#knock off anything not in
                        ustring = " ".join(ustring)#accepted, replace by whitespace
                        
        ustring = ustring.split()#then split on whitespace
                       
        ustring = [float(num) for num in ustring]#make sure numbers are decimals
        
        return ustring

def alternativeconvert(ustring):
        """Formats through regular expression."""
        pat = re.compile('[^0-9.]')#import re..
        ustring = re.split(pat, ' ', ustring)
        ustring = ustring.split()
        ustring = [decimal.Decimal(num) for num in ustring]#import decimal..
        return ustring
        
def getxlist(firstlist):
        lx = []
        if firstlist:
                lx = [firstlist[0]] + getxlist(firstlist[2:])         
        return lx               

def getylist(firstlist):
        ly = []
        if firstlist:
                ly = [firstlist[1]] + getylist(firstlist[2:])
        return ly
        
def getxnylist(firstlist):
        """Creates two lists. Each list has one out of two elements of the first list.
        
        The first list will represent x-values, the second  y-values."""
        lx = getxlist(firstlist)
        ly = getylist(firstlist)
        if len(lx) != len(ly):
            print "Missing coordinates.. Make sure you have pairs."
            sys.exit()
        else:
            pass
        return lx, ly                  
        
def listsqsum(l):
        """Sums the squares of the elements of a list."""
        total = 0
        if l:
                total = (l[0])**2 + listsqsum(l[1:])
        return total
        
def listxysum(l):
        """Sums the product of the l-list elements two by two."""
        total = 0
        if l:
                total = l[0]*l[1] + listxysum(l[2:])
        return total
        
if __name__ == "__main__":
        main()

        
#TODO:
#code a general summation function --> summation(expression, indexstart, indexstop)
#as yet one can only calculate y=b1+b2x --> allow for different transformations on x
#expand simple linear regression to multiple regression
#add standard errors, R**2 and other interesting values

#def summation(expr, i=0, n):

Excellent!

Merci!

Je me sens pousser une langue fourchue et un corps glissant! Ca va pythonner!

Peace,