Python - "cannot Perform Reduce With Flexible Type" When Trying To Use Numpy.mean

I'm at my wit's end as I keep getting 'cannot perform reduce with flexible type' when I try to compute the mean of a column, the file is read in just fine (no missing values in any

Solution 1:

When you're working with structured arrays like that you lose some of the flexibility you'd otherwise have. You can take the mean after selecting the appropriate piece, though:

>>> ifile
array([(3.385, 44.5), (0.48, 15.5), (1.35, 8.1), (465.0, 423.0),
       (36.33, 119.5), (27.66, 115.0), (14.83, 98.2), (1.04, 5.5)], 
      dtype=[('brainwt', '<f8'), ('bodywt', '<f8')])
>>> ifile["brainwt"].mean()
68.759375000000006
>>> ifile["bodywt"].mean()
103.66249999999999

---

I use numpy almost every day, but when working with data of the sort where I want to name columns, I think the pandas library makes things much more convenient, and it interoperates very well. It's worth a look. Example:

>>> import pandas as pd
>>> df = pd.read_csv("brainandbody.csv", skipinitialspace=True)
>>> df
   Brain Weight  Body Weight
0         3.385         44.5
1         0.480         15.5
2         1.350          8.1
3       465.000        423.0
4        36.330        119.5
5        27.660        115.0
6        14.830         98.2
7         1.040          5.5
>>> df.mean()
Brain Weight     68.759375
Body Weight     103.662500
dtype: float64