How to convert an array of strings to an array of floats in numpy?
How to convert
["1.1", "2.2", "3.2"]
[1.1, 2.2, 3.2]
Well, if you're reading the data in as a list, just do
np.array(map(float, list_of_strings)) (or equivalently, use a list comprehension). (In Python 3, you'll need to call
list on the
map return value if you use
map returns an iterator now.)
However, if it's already a numpy array of strings, there's a better way. Use
import numpy as np x = np.array(['1.1', '2.2', '3.3']) y = x.astype(np.float)
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You can use this as well
import numpy as np x=np.array(['1.1', '2.2', '3.3']) x=np.asfarray(x,float)
Another option might be numpy.asarray:
import numpy as np a = ["1.1", "2.2", "3.2"] b = np.asarray(a, dtype=np.float64, order='C')
For Python 2*:
print a, type(a), type(a) print b, type(b), type(b)
['1.1', '2.2', '3.2'] <type 'list'> <type 'str'> [1.1 2.2 3.2] <type 'numpy.ndarray'> <type 'numpy.float64'>
If you have (or create) a single string, you can use np.fromstring:
import numpy as np x = ["1.1", "2.2", "3.2"] x = ','.join(x) x = np.fromstring( x, dtype=np.float, sep=',' )
x = ','.join(x) transforms the x array to string
'1.1, 2.2, 3.2'. If you read a line from a txt file, each line will be already a string.