The object returned by maskedArray.compressed() appears to be a normal numpy array (based on repr output), but in reality it has some surprising differences:
import numpy a = numpy.arange(10, dtype=int) b = numpy.zeros(10) b[1] = 1 b[3] = 1 ma = numpy.core.ma.array(a, mask=b, dtype=float) print ma # [0.0 -- 2.0 -- 4.0 5.0 6.0 7.0 8.0 9.0] c = ma.compressed() print repr(c) # array([ 0. 2. 4. 5. 6. 7. 8. 9.]) c.sort() #Traceback (most recent call last): # File "<stdin>", line 1, in <module> # File "/Library/Frameworks/Python.framework/Versions/2.5/lib/python2.5/site-pac kages/#numpy/core/ma.py", line 2132, in not_implemented # raise NotImplementedError, "not yet implemented for numpy.ma arrays" #NotImplementedError: not yet implemented for numpy.ma arrays d = numpy.array(c) d.sort() # this works fine, as expected Why is "c" in the example above not just a regular numpy array? It is not a "live" view (based on a quick test), which seems sensible to me. I've worked around the problem by making a copy (d in the example above), but it seems most unfortunate to have to copy the data twice. -- Russsell _______________________________________________ Numpy-discussion mailing list Numpy-discussion@scipy.org http://projects.scipy.org/mailman/listinfo/numpy-discussion
