Implementing logistic regression
This is very similar to the earlier exercise where you implemented linear regression "from scratch" using scipy.optimize.minimize. However, this time we'll minimize the logistic loss and compare with scikit-learn's LogisticRegression (we've set C to a large value to disable regularization; more on this in Chapter 3!).
The log_loss() function from the previous exercise is already defined in your environment, and the sklearn breast cancer prediction dataset (first 10 features, standardized) is loaded into the variables X and y.
Deze oefening maakt deel uit van de cursus
Linear Classifiers in Python
Oefeninstructies
- Input the number of training examples into
range(). - Fill in the loss function for logistic regression.
- Compare the coefficients to sklearn's
LogisticRegression.
Praktische interactieve oefening
Probeer deze oefening eens door deze voorbeeldcode in te vullen.
# The logistic loss, summed over training examples
def my_loss(w):
s = 0
for i in range(____):
raw_model_output = w@X[i]
s = s + ____(raw_model_output * y[i])
return s
# Returns the w that makes my_loss(w) smallest
w_fit = minimize(my_loss, X[0]).x
print(w_fit)
# Compare with scikit-learn's LogisticRegression
lr = LogisticRegression(fit_intercept=False, C=1000000).fit(X,y)
print(lr.coef_)