Data structure and usage without a dongle

[bp96]

Hi,
I am new to this but was wondering if you could tell me a little bit more about what the structure of the numpy files is for the training data (is it the phase of the signals, or just their frequencies?).

Also, I am trying to run the train_keras code using the numpy files already provided to test out the frequencies at the bottom of the code (without having a rtl-sdr dongle present and on Ubuntu 18.04). Is this possible to do since I seem to get the following error:

Traceback (most recent call last):
  File "/home/usr/cnn-rtlsdr-master/train_keras.py", line 83, in <module>
    sdr = RtlSdr()

  File "/home/usr/env/test/lib/python3.6/site-packages/rtlsdr/rtlsdr.py", line 133, in __init__
    self.open(device_index, test_mode_enabled, serial_number)

  File "/home/usr/env/test/lib/python3.6/site-packages/rtlsdr/rtlsdr.py", line 172, in open
    % (result, device_index))

OSError: Error code -1 when opening SDR (device index = 0)
[Finished in 12.6s with exit code 1]