[Numpy-discussion] Using objects in arrays

Sue Giller sag at hydrosphere.com
Tue Dec 4 09:28:07 CST 2001


I am trying to use objects in an array, and still be able to use the 
various extra functions offered by multiarray.  I am finding that some 
of the functions work and some don't.  Is it hopeless to try to use 
objects in an array and expect <op>.reduce and others to work 
properly?

As a simple example, I have a DataPoint object that consists of a 
value and flag(s).  This object has all the __cmp__, __add_, etc 
functions implemented.

I can do MA.average(m), MA.sum(m), MA.add.reduce(m), (they 
seem to use __add__) but I can't do MA.minimum.reduce(m) or 
MA.maximum.reduce(m).

I can do MA.maximum(m) and MA.minimum(m), but not 
MA.maximum(m, 0) or MA.minimum(m, 0)

The values returned by MA.argmax(m) makes no sense (wrong 
index?) but is consistent with results from argsort().   MA.argmin(m) 
gives an error (I have a __neg__ fn in datapoint)
	File "C:\Python21\MA\MA.py", line 1977, in argmin	 
                   return Numeric.argmin(d, axis)
	File "C:\Python21\Numeric\Numeric.py", line 281, in argmin
			 a = -array(a, copy=0)
	TypeError: bad operand type for unary -

for example:
	  print m					# 3 valid, 1 masked
        print MA.maximum(m)
        print MA.argmax(m)		# gives index to masked value
        print MA.minimum(m)
	  #print MA.argmin(m)        - gives error above
        print MA.argsort(m)
        print MA.average(m)
        print MA.maximum.reduce(m, 0)

[1, ] ,[10, a] ,[None, D] ,-- ,]
[10, a]
3
[None, D]
[2,0,1,3,]
[3.66666666667, aD]
Traceback (most recent call last):
  File "C:\Python21\Pythonwin\pywin\framework\scriptutils.py", line 
301, in RunScript
    exec codeObject in __main__.__dict__
  File "C:\Python21\HDP\Data\DataPoint.py", line 136, in ?
    print MA.maximum.reduce(m, 0)
  File "C:\Python21\MA\MA.py", line 1913, in reduce
    t = Numeric.maximum.reduce(filled(target, 
maximum_fill_value(target)), axis)
TypeError: function not supported for these types, and can't coerce 
to supported types 




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