I can't seem to convert it into an ndarray
in numpy, i've read http://docs.scipy.org/doc/numpy/reference/generated/numpy.ndarray.html but it didn't show me how i can convert my input data as shown below into an ndarray
.
How to construct a ndarray from a numpy array or a list of integer lists? * What's the difference between ndarray and array? * I could just use an array
type right?
I have a list of integer counts like this
[[1, 2, 4, 1, 5],
[6, 0, 0, 0, 2],
[0, 0, 0, 1, 0]]
And i manage to use this code to create a np.array
as shown in http://docs.scipy.org/doc/numpy/reference/generated/numpy.array.html#numpy.array
import numpy as np
x = [[1, 2, 4, 1, 5],
[6, 0, 0, 0, 2],
[0, 0, 0, 1, 0]]
print np.array(x)
[out]:
[[1 2 4 1 5]
[6 0 0 0 2]
[0 0 0 1 0]]
But I can't change it into a np.ndarray
with this code:
import numpy as np
x = [[1, 2, 4, 1, 5],
[6, 0, 0, 0, 2],
[0, 0, 0, 1, 0]]
print np.ndarray(x)
I got an error:
Traceback (most recent call last):
File "/home/alvas/workspace/sklearntut/test.py", line 7, in <module>
print np.ndarray(x)
TypeError: an integer is required
How do I create a np.ndarray with the list of integer counts i've got? What integer is the TypeError talking about?
An ndarray
is a NumPy array.
>>> x = np.array([1, 2, 3])
>>> type(x)
<type 'numpy.ndarray'>
The difference between np.ndarray
and np.array
is that the former is the actual type, while the latter is a flexible shorthand function for constructing arrays from data in other formats. The TypeError
comes your use of np.array
arguments to np.ndarray
, which takes completely different arguments (see docstrings).
Though the accepted response is correct, that didn't help me actually create a 1-dimensional array of arrays.
As this thread is the first answer at Google, I post my work around, even if it isn't elegant solution (please don't hesitate to point one out to me):
import numpy as np
# Create example array
initial_array = np.ones(shape = (2,2))
# Create array of arrays
array_of_arrays = np.ndarray(shape = (1,), dtype = "object")
array_of_arrays[0] = initial_array
Be aware that array_of_arrays
is in this case mutable, ie changing initial_array
automatically changes array_of_arrays
.
I will combine the accepted solution with the fixed code. As said in the accepted solution, an ndarray
is a NumPy array
.
This essentially means that you should use np.array
when constructing an ndarray from a list of lists, a list of tuples, a tuple of lists...
Fixed code fragment:
import numpy as np
x = [[1, 2, 4, 1, 5],
[6, 0, 0, 0, 2],
[0, 0, 0, 1, 0]]
# The difference: we call np.array
print np.array(x)
Hope this will help others out as this is the first Google answer.
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