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index_tricks.py
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index_tricks.py
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import types
import Numeric
__all__ = ['mgrid','r_','c_','index_exp']
from type_check import ScalarType
class nd_grid:
""" Construct a "meshgrid" in N-dimensions.
grid = nd_grid() creates an instance which will return a mesh-grid
when indexed. The dimension and number of the output arrays are equal
to the number of indexing dimensions. If the step length is not a complex
number, then the stop is not inclusive.
However, if the step length is a COMPLEX NUMBER (e.g. 5j), then the integer
part of it's magnitude is interpreted as specifying the number of points to
create between the start and stop values, where the stop value
IS INCLUSIVE.
Example:
>>> mgrid = nd_grid()
>>> mgrid[0:5,0:5]
array([[[0, 0, 0, 0, 0],
[1, 1, 1, 1, 1],
[2, 2, 2, 2, 2],
[3, 3, 3, 3, 3],
[4, 4, 4, 4, 4]],
[[0, 1, 2, 3, 4],
[0, 1, 2, 3, 4],
[0, 1, 2, 3, 4],
[0, 1, 2, 3, 4],
[0, 1, 2, 3, 4]]])
>>> mgrid[-1:1:5j]
array([-1. , -0.5, 0. , 0.5, 1. ])
"""
def __getitem__(self,key):
try:
size = []
typecode = Numeric.Int
for k in range(len(key)):
step = key[k].step
start = key[k].start
if start is None: start = 0
if step is None:
step = 1
if type(step) is type(1j):
size.append(int(abs(step)))
typecode = Numeric.Float
else:
size.append(int((key[k].stop - start)/(step*1.0)))
if isinstance(step,types.FloatType) or \
isinstance(start, types.FloatType) or \
isinstance(key[k].stop, types.FloatType):
typecode = Numeric.Float
nn = Numeric.indices(size,typecode)
for k in range(len(size)):
step = key[k].step
if step is None:
step = 1
if type(step) is type(1j):
step = int(abs(step))
step = (key[k].stop - key[k].start)/float(step-1)
nn[k] = (nn[k]*step+key[k].start)
return nn
except (IndexError, TypeError):
step = key.step
stop = key.stop
start = key.start
if start is None: start = 0
if type(step) is type(1j):
step = abs(step)
length = int(step)
step = (key.stop-start)/float(step-1)
stop = key.stop+step
return Numeric.arange(0,length,1,Numeric.Float)*step + start
else:
return Numeric.arange(start, stop, step)
def __getslice__(self,i,j):
return Numeric.arange(i,j)
def __len__(self):
return 0
mgrid = nd_grid()
class concatenator:
""" Translates slice objects to concatenation along an axis.
"""
def __init__(self, axis=0):
self.axis = axis
def __getitem__(self,key):
if type(key) is not types.TupleType:
key = (key,)
objs = []
for k in range(len(key)):
if type(key[k]) is types.SliceType:
typecode = Numeric.Int
step = key[k].step
start = key[k].start
stop = key[k].stop
if start is None: start = 0
if step is None:
step = 1
if type(step) is type(1j):
size = int(abs(step))
typecode = Numeric.Float
endpoint = 1
else:
size = int((stop - start)/(step*1.0))
endpoint = 0
if isinstance(step,types.FloatType) or \
isinstance(start, types.FloatType) or \
isinstance(stop, types.FloatType):
typecode = Numeric.Float
newobj = linspace(start, stop, num=size, endpoint=endpoint)
elif type(key[k]) in ScalarType:
newobj = Numeric.asarray([key[k]])
else:
newobj = key[k]
objs.append(newobj)
return Numeric.concatenate(tuple(objs),axis=self.axis)
def __getslice__(self,i,j):
return Numeric.arange(i,j)
def __len__(self):
return 0
r_=concatenator(0)
c_=concatenator(-1)
# A nicer way to build up index tuples for arrays.
#
# You can do all this with slice() plus a few special objects,
# but there's a lot to remember. This version is simpler because
# it uses the standard array indexing syntax.
#
# Written by Konrad Hinsen <hinsen@cnrs-orleans.fr>
# last revision: 1999-7-23
#
# Cosmetic changes by T. Oliphant 2001
#
#
# This module provides a convenient method for constructing
# array indices algorithmically. It provides one importable object,
# 'index_expression'.
#
# For any index combination, including slicing and axis insertion,
# 'a[indices]' is the same as 'a[index_expression[indices]]' for any
# array 'a'. However, 'index_expression[indices]' can be used anywhere
# in Python code and returns a tuple of slice objects that can be
# used in the construction of complex index expressions.
class _index_expression_class:
import sys
maxint = sys.maxint
def __getitem__(self, item):
if type(item) != type(()):
return (item,)
else:
return item
def __len__(self):
return self.maxint
def __getslice__(self, start, stop):
if stop == self.maxint:
stop = None
return self[start:stop:None]
index_exp = _index_expression_class()
# End contribution from Konrad.