Non Negative Values in Y

Is there a reason why if Y has no negative an error is returned.

>>> x = range(2,20)
>>> y=[]
>>> for i in x:
...     y.append(i*100)
>>> x
[2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19]
>>> y
[200, 300, 400, 500, 600, 700, 800, 900, 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1700, 1800, 1900]
>>> 
>>> kneed.KneeLocator(x,y)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/kneed/knee_locator.py", line 61, in __init__
    self.knee, self.norm_knee, self.knee_x = self.find_knee()
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/kneed/knee_locator.py", line 74, in find_knee
    mxmx_iter = np.arange(self.xmx_idx[0], len(self.xsn))
IndexError: index 0 is out of bounds for axis 0 with size 0

>>> y[0]=-1
>>> kneed.KneeLocator(x,y)
<kneed.knee_locator.KneeLocator object at 0x106a56d10>

[raviolli]

Solution Solved. Update from github rather then pip default repo

[arvkevi]

@raviolli the example you provided didn’t have a local maximum, which caused the error. See the image below, b383b0b includes a print statement informing the user that no maxima was found and returns None for the knee so the user can inspect the function.