title: Python SMOTE applied to extracted signals (arrays) of different size
body: <p>I'm unable to create new minority class instances to balance my data.
  My signals have different sizes which I think is the problem.
  I was aiming to try transformation in frequency domain to get a fixed array size and found out I got the same error I got from SMOTE:</p>
  <pre><code>---------------------------------------------------------------------------
  TypeError                                 Traceback (most recent call last)
  TypeError: only size-1 arrays can be converted to Python scalars
  
  The above exception was the direct cause of the following exception:
  
  ValueError                                Traceback (most recent call last)
  &lt;ipython-input-318-0ab6c9eba330&gt; in &lt;module&gt;
  ----&gt; 1 saved_data11 = fft(saved_data1)
  
  C:\ProgramData\Anaconda3\lib\site-packages\scipy\fft\_backend.py in __ua_function__(method, args, kwargs)
       21         if fn is None:
       22             return NotImplemented
  ---&gt; 23         return fn(*args, **kwargs)
       24 
       25 
  
  C:\ProgramData\Anaconda3\lib\site-packages\scipy\fft\_pocketfft\basic.py in c2c(forward, x, n, axis, norm, overwrite_x, workers, plan)
       15         raise NotImplementedError('Passing a precomputed plan is not yet '
       16                                   'supported by scipy.fft functions')
  ---&gt; 17     tmp = _asfarray(x)
       18     overwrite_x = overwrite_x or _datacopied(tmp, x)
       19     norm = _normalization(norm, forward)
  
  C:\ProgramData\Anaconda3\lib\site-packages\scipy\fft\_pocketfft\helper.py in _asfarray(x)
       90         return np.asarray(x, np.float32)
       91     elif x.dtype.kind not in 'fc':
  ---&gt; 92         return np.asarray(x, np.float64)
       93 
       94     # Require native byte order
  
  C:\ProgramData\Anaconda3\lib\site-packages\numpy\core\_asarray.py in asarray(a, dtype, order, like)
      100         return _asarray_with_like(a, dtype=dtype, order=order, like=like)
      101 
  --&gt; 102     return array(a, dtype, copy=False, order=order)
      103 
      104 
  
  ValueError: setting an array element with a sequence.
  </code></pre>
  <p>I think the way I extracted the signals (appending signal to list) might be the reason for this problem but I am unable to find a fitting solution.</p>
  <pre><code># pre-processing
  signal = 0.90 * (signal/abs(max(signal)))
  #remove silence
  signal = svt.rms_silence_filter(signal, threshold=0.005)
  
  # I am trying to save the signal after the pre-processing.
  saved_data.append(np.array(signal))
  saved_names.append(variable + '-'+ files[j])
  print(count, end = ' ')
  count += 1
  </code></pre>