CODEWITHSUNDEEP
pythonarraysnumpy
p.in4matics
p.in4matics

Reputation: 97

Sorting numpy array with np.lexsort containing float values

I am writing a program to sort the names of amino acids depending on their energy value within a particular company.

I have extracted relevant data to the following numpy array.

And I tried this

In[37]: Data = np.array([
 ['ASN 205', -9.64164],
 ['LEU 206', -8.985774],
 ['ASN 207', -7.314434],
 ['PRO 208', -4.105338],
 ['ASN 209', -2.092342],
 ['GLY 210', -2.101412],
 ['LYS 211', -2.483852],
 ['ARG 212', -24.20364],
 ['SER 213', -1.181002],
 ['VAL 214', 0.057618]])
In[38]: ind3 = np.lexsort((Data[:,0],Data[:,1]))
In[39]: Result = Data[ind3]
In[40]: Result
Out[40]: 
array([['SER 213', '-1.181002'],
       ['ASN 209', '-2.092342'],
       ['GLY 210', '-2.101412'],
       ['LYS 211', '-2.483852'],
       ['ARG 212', '-24.20364'],
       ['PRO 208', '-4.105338'],
       ['ASN 207', '-7.314434'],
       ['LEU 206', '-8.985774'],
       ['ASN 205', '-9.64164'],
       ['VAL 214', '0.057618']], 
      dtype='|S9')

But the problem here is float values are arranged in a lexicographic way. I want it be be ordered according to their value means -24.20364 first then ...-2.483852.

How do I do this?

Upvotes: 1

Views: 863

Answers (1)

marc
marc

Reputation: 6223

explanation: np.array converts all the passed arguments to the biggest type fitting all arguments, i.e. your float get converted in line 1. You can instead use tuples with a specific data type as follows:

Data = np.array([
 ('ASN 205', -9.64164),
 ('LEU 206', -8.985774),
 ('ASN 207', -7.314434),
 ('PRO 208', -4.105338),
 ('ASN 209', -2.092342),
 ('GLY 210', -2.101412),
 ('LYS 211', -2.483852),
 ('ARG 212', -24.20364),
 ('SER 213', -1.181002),
 ('VAL 214', 0.057618)], dtype=[('f', '|S9'), ('g', float)])
ind3 = np.lexsort((Data['f'], Data['g']))
Result = Data[ind3]Out[8]:

output:

array([('ARG 212', -24.20364), ('ASN 205', -9.64164),
       ('LEU 206', -8.985774), ('ASN 207', -7.314434),
       ('PRO 208', -4.105338), ('LYS 211', -2.483852),
       ('GLY 210', -2.101412), ('ASN 209', -2.092342),
       ('SER 213', -1.181002), ('VAL 214', 0.057618)], 
      dtype=[('f', 'S9'), ('g', '<f8')])

Upvotes: 2

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