Identifying the start of good data in a list

Gerard flanagan grflanagan at gmail.com
Wed Aug 27 21:00:46 CEST 2008


tkpmep at hotmail.com wrote:
> I have a list that starts with zeros, has sporadic data, and then has
> good data. I define the point at  which the data turns good to be the
> first index with a non-zero entry that is followed by at least 4
> consecutive non-zero data items (i.e. a week's worth of non-zero
> data). For example, if my list is [0, 0, 1, 0, 1, 2, 3, 4, 5, 6, 7, 8,
> 9], I would define the point at which data turns good to be 4 (1
> followed by 2, 3, 4, 5).
> 
> I have a simple algorithm to identify this changepoint, but it looks
> crude: is there a cleaner, more elegant way to do this?
> 
>     flag = True
>     i=-1
>     j=0
>     while flag and i < len(retHist)-1:
>         i += 1
>         if retHist[i] == 0:
>             j = 0
>         else:
>             j += 1
>             if j == 5:
>                 flag = False
> 
>     del retHist[:i-4]
> 
> Thanks in advance for your help
> 
> Thomas Philips



data = [0, 0, 1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9]


def itergood(indata):
     indata = iter(indata)
     buf = []
     while len(buf) < 4:
         buf.append(indata.next())
         if buf[-1] == 0:
             buf[:] = []
     for x in buf:
         yield x
     for x in indata:
         yield x


for d in itergood(data):
     print d




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