Dirk Nachbar wrote:
> Here is a function which takes any list and creates a freq table,
> which can be printed unsorted, sorted by cases or items. It's supposed
> to mirror the proc freq in SAS.
>
> Dirk
>
> def freq(seq,order='unsorted',prin=True):
> #order can be unsorted, cases, items
>
> freq={}
> for s in seq:
> if s in freq:
> freq[s]+=1
> else:
> freq[s]=1
> if prin==True:
> print 'Items=',len(seq),'Cases=',len(freq)
> print '------------------------'
> if order=='unsorted':
> for k in freq.keys():
> print k,freq[k],float(freq[k])/len(seq)
> elif order=='cases':
> #http://blog.client9.com/2007/11/sorting-python-dict-by-
> value.html
> freq2=sorted(freq.iteritems(), key=lambda (k,v):
> (v,k),reverse=True)
Sorting in two steps gives a slightly better result when there are items
with equal keys. Compare
>>> freq = {"a": 2, "b": 1, "c": 1, "d": 2}
>>> sorted(freq.iteritems(), key=lambda (k, v): (v, k), reverse=True)
[('d', 2), ('a', 2), ('c', 1), ('b', 1)]
with
>>> freq2 = sorted(freq.iteritems(), key=lambda (k, v): k)
>>> freq2.sort(key=lambda (k, v): v, reverse=True)
>>> freq2
[('a', 2), ('d', 2), ('b', 1), ('c', 1)]
Here the keys within groups of equal frequency are in normal instead of
reversed order.
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