Returning index of DataFrame pandas

Question

I got the following DataFrame:

System             R    System_num
0    CO           0.8           1
1    CO           0.9           1
2    CO           1.0           1
3    CO           1.2           1
4    CO           1.4           1
5    CO           0.8           2
6    CO           0.9           2
7    CO           1.0           2
8    CO           1.2           2
9    CO           1.4           2
10   CO           0.8           3

I would like to return the index of the line for which R = 1.4 and System_num = 2. I've tried by:

df.ix[df.System_num == 2 & df.R == 1.4].index

Though the error message is returning:

print df.ix[df.System_num == 2 & df.R == 1.4].index

     File "/apps/anaconda/lib/python2.7/site-packages/pandas/core/ops.py", line 834, in wrapper
        na_op(self.values, other),
      File "/apps/anaconda/lib/python2.7/site-packages/pandas/core/ops.py", line 805, in na_op
        x.dtype, type(y).__name__))
    TypeError: cannot compare a dtyped [float64] array with a scalar of type [bool]

What am I doing wrong?

df.ix[(df.System_num == 2) & (df.R == 1.4)].index you need parenthesis around the comparison also see here. — akuiper
– akuiper, Commented Jan 19, 2017 at 15:05

Blackecho · Accepted Answer · 2017-01-19 15:07:13Z

2

You should use parentheses with the & operator. Check out pandas documentation for indexing data. It says:

Another common operation is the use of boolean vectors to filter the data. The operators are: | for or, & for and, and ~ for not. These must be grouped by using parentheses.

answered Jan 19, 2017 at 15:07

Blackecho

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