Numpy array from int to float

Question

I have this code to extract some data from a csv. I can extract the data with no problem but I would like to change the numpy array from a int to a float. I know that the argument to do that is dtype=np.float32 but I keep having an error message when I do include this argument: This is the code:

import numpy as np
import pandas as pd
rainfall=pd.read_csv('Seattle2014.csv')['PRCP'].values
inches=rainfall / 254
inches.shape

#...

rainy=(inches >0)
summer=(np.arange(365)-172<90) &(np.arange(365)-172>0)
print ("Mediam precipitation on rainy days in 2014  (inches):       ",np.median(inches[rainy]))
print ("Mediam precipitation on summer days in 2014 (inches):       ",np.median(inches[summer]))
print ("Maximum precipitation on summer days in 2014 (inches):      ",np.max(inches[summer]))
print ("Median precipitation on non-summer days in 2014 (inches):  ",np.median(inches[rainy & ~summer]))

This is the code with the argument:

rainy=(inches >0)
summer=(np.arange(365)-172<90) &(np.arange(365)-172>0)
print ("Mediam precipitation on rainy days in 2014  (inches):       ",np.median(inches[rainy], dtype=float))

And I do get this error message:

TypeErrorTraceback (most recent call last) <ipython-input-136-29b7a435cc0e> in <module>()
      1 rainy=(inches >0)
      2 summer=(np.arange(365)-172<90) &(np.arange(365)-172>0)
----> 3 print ("Mediam precipitation on rainy days in 2014  (inches):       ",np.median(inches[rainy], dtype=float))
      4 print ("Mediam precipitation on summer days in 2014 (inches):       ",np.median(inches[summer]))
      5 print ("Maximum precipitation on summer days in 2014 (inches):      ",np.max(inches[summer]))

TypeError: median() got an unexpected keyword argument 'dtype'

How can I solve this problem?

"I know that the argument to do that is dtype=np.float32" no---that's the argument to specify the type when you create the array. The median function has no such keyword argument, as the docs show. It's a single element anyways right? Just use float(...). — alkasm
– alkasm, Commented Feb 17, 2019 at 12:01
Also it's unclear why you're using numpy to do the manipulations since you originally read in a dataframe from pandas. Just use the .median() and .max() and so on methods on the dataframe? You can print whatever representation you choose regardless. — alkasm
– alkasm, Commented Feb 17, 2019 at 12:05
@AlexanderReynolds I am trying to follow an exercise in "Python Data Science Handbook", the exercise starts around page 70 and goes to 74-76. The csv file is a download from the github page related to the book. In the book, the solution are presented as float but when I do it I get integers. I must be something missing or the csv file used for the book is different than the one in github. — Ana
– Ana, Commented Feb 17, 2019 at 15:59
How about just changing the rainfall data to float directly: rainfall=pd.read_csv('Seattle2014.csv')['PRCP'].values.astype(np.float) — Tarifazo
– Tarifazo, Commented Feb 17, 2019 at 16:48

Community · Accepted Answer · 2020-06-20 09:12:55Z

1

numpy.median() has no argument dtype. This is its output behaviour:

RETURNS: median : ndarray

A new array holding the result (unless out is specified, in which case that array is returned instead). If the input contains integers, or floats of smaller precision than 64, then the output data-type is float64. Otherwise, the output data-type is the same as that of the input.

edited Jun 20, 2020 at 9:12

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