Read binary file to array of complex numbers

Question

I have a binary file written as

16b-Real (little endian, 2s compliment)
16b-Imag (little endian, 2s compliment)
.....repeating

I need to convert it to a 1D array of complex numbers. Can't figure out how to combine the "tuples or lists" into a single value

import numpy as np
dtype = np.dtype([('i','<i2'), ('q','<i2')])
array = np.fromfile(data_file, dtype=dtype)
print(array)
el = array[0]
print(el)
print(type(el))

Output:

[(531, -660) (267, -801) (-36, -841) ... (835, -102) (750, -396)
 (567, -628)]
(531, -660)
<class 'numpy.void'>

Hoping for output:

[531-660j, 267-801j,...]

can you give us an example of actual input (and not just the format?) I'm not sure I fully understand the format of your input, which may be a part of the problem. — David Culbreth
– David Culbreth, Commented Jul 17, 2019 at 19:52
Input binary data from hex editor grouped by bytes: 13 02 6C FD 0B 01 DF FC. Which when grouped by word looks like: 0213 FD6C 010B FCDF. In decimal: 531 -660 267 -801 — Borisw37
– Borisw37, Commented Jul 17, 2019 at 19:58

Devesh Kumar Singh · Accepted Answer · 2019-07-17 19:53:15Z

3

You can convert each tuple to a complex number while iterating over the list of tuples

array = [(531, -660), (267, -801), (-36, -841) ,(835, -102) ,(750, -396), (567, -628)]

#Iterate over each element and convert it to complex
array = [complex(*item) for item in array]

print(array)
print(type(array[0]))

The output will be

[(531-660j), (267-801j), (-36-841j), (835-102j), (750-396j), (567-628j)]
<class 'complex'>

answered Jul 17, 2019 at 19:53

Devesh Kumar Singh

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Comments

hpaulj · Accepted Answer · 2019-07-17 20:39:07Z

So you have loaded the file as a structured array with 2 integer fields:

In [71]: dtype = np.dtype([('i','<i2'), ('q','<i2')])                                                        
In [72]: arr = np.array([(531, -660), (267, -801), (-36, -841), (835, -102), (750, -396)], dtype)            
In [73]: arr                                                                                                 
Out[73]: 
array([(531, -660), (267, -801), (-36, -841), (835, -102), (750, -396)],
      dtype=[('i', '<i2'), ('q', '<i2')])

We can add the two fields with the appropriate 1j multiplier to make a complex array:

In [74]: x=arr['i']+1j*arr['q']                                                                              
In [75]: x                                                                                                   
Out[75]: array([531.-660.j, 267.-801.j, -36.-841.j, 835.-102.j, 750.-396.j])

If I'm not mistaken, numpy only implements float complex (64 and 128 bit), so probably have go through this <i2 stage.

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