I have a three-class problem and I'm able to report precision and recall for each class with the below code:
from sklearn.metrics import classification_report
print(classification_report(y_test, y_pred))
which gives me the precision and recall nicely for each of the 3 classes in a table format.
My question is how can I now get sensitivity and specificity for each of the 3 classes? I looked at sklearn.metrics and I didn't find anything for reporting sensitivity and specificity.
If we check the help page for classification report:
Note that in binary classification, recall of the positive class is also known as “sensitivity”; recall of the negative class is “specificity”.
So we can convert the pred into a binary for every class, and then use the recall results from precision_recall_fscore_support.
Using an example:
from sklearn.metrics import classification_report
y_true = [0, 1, 2, 2, 2]
y_pred = [0, 0, 2, 2, 1]
target_names = ['class 0', 'class 1', 'class 2']
print(classification_report(y_true, y_pred, target_names=target_names))
Looks like:
precision recall f1-score support
class 0 0.50 1.00 0.67 1
class 1 0.00 0.00 0.00 1
class 2 1.00 0.67 0.80 3
accuracy 0.60 5
macro avg 0.50 0.56 0.49 5
weighted avg 0.70 0.60 0.61 5
Using sklearn:
from sklearn.metrics import precision_recall_fscore_support
res = []
for l in [0,1,2]:
prec,recall,_,_ = precision_recall_fscore_support(np.array(y_true)==l,
np.array(y_pred)==l,
pos_label=True,average=None)
res.append([l,recall[0],recall[1]])
put the results into a dataframe:
pd.DataFrame(res,columns = ['class','sensitivity','specificity'])
class sensitivity specificity
0 0 0.75 1.000000
1 1 0.75 0.000000
2 2 1.00 0.666667