Probably there's something wrong with the input values for X and/or T. The function from the question works ok:
import numpy as np
from math import e
def sigmoid(X, T):
return 1.0 / (1.0 + np.exp(-1.0 * np.dot(X, T)))
X = np.array([[1, 2, 3], [5, 0, 0]])
T = np.array([[1, 2], [1, 1], [4, 4]])
print(X.dot(T))
# Just to see if values are ok
print([1. / (1. + e ** el) for el in [-5, -10, -15, -16]])
print()
print(sigmoid(X, T))
Result:
[[15 16]
[ 5 10]]
[0.9933071490757153, 0.9999546021312976, 0.999999694097773, 0.9999998874648379]
[[ 0.99999969 0.99999989]
[ 0.99330715 0.9999546 ]]
Probably it's the dtype of your input arrays. Changing X to:
X = np.array([[1, 2, 3], [5, 0, 0]], dtype=object)
Gives:
Traceback (most recent call last):
File "/[...]/stackoverflow_sigmoid.py", line 24, in <module>
print sigmoid(X, T)
File "/[...]/stackoverflow_sigmoid.py", line 14, in sigmoid
return 1.0 / (1.0 + np.exp(-1.0 * np.dot(X, T)))
AttributeError: exp