[Numpy-discussion] apply table lookup to each element

Neal Becker ndbecker2@gmail....
Fri May 1 13:28:48 CDT 2009


Suggestion for efficient way to apply a table lookup to each element of an 
integer array?

import numpy as np
_cos = np.empty ((2**rom_in_bits,), dtype=int)
_sin = np.empty ((2**rom_in_bits,), dtype=int)
for address in xrange (2**12):
    _cos[address] = nint ((2.0**(rom_out_bits-1)-1) * cos (2 * pi * address 
* (2.0**-rom_in_bits)))
    _sin[address] = nint ((2.0**(rom_out_bits-1)-1) * sin (2 * pi * address 
* (2.0**-rom_in_bits)))

Now _cos, _sin are arrays of integers (quantized sin, cos lookup tables)

How to apply _cos lookup to each element of an integer array:

phase = np.array (..., dtype =int)
cos_out = lookup (phase, _cos) ???




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