Fbeta#

ignite.metrics.Fbeta(beta, average=True, precision=None, recall=None, output_transform=None, device=device(type='cpu'))[source]#

Calculates F-beta score.

F_\beta = \left( 1 + \beta^2 \right) * \frac{ \text{precision} * \text{recall} } { \left( \beta^2 * \text{precision} \right) + \text{recall} }

where $\beta$ is a positive real factor.

update must receive output of the form (y_pred, y).
y_pred must be in the following shape (batch_size, num_categories, …) or (batch_size, …).
y must be in the following shape (batch_size, …).

Parameters

beta (float) – weight of precision in harmonic mean
average (bool) – if True, F-beta score is computed as the unweighted average (across all classes in multiclass case), otherwise, returns a tensor with F-beta score for each class in multiclass case.
precision (Optional[Precision]) – precision object metric with average=False to compute F-beta score
recall (Optional[Recall]) – recall object metric with average=False to compute F-beta score
output_transform (Optional[Callable]) – a callable that is used to transform the Engine’s process_function’s output into the form expected by the metric. It is used only if precision or recall are not provided.
device (Union[str, device]) – specifies which device updates are accumulated on. Setting the metric’s device to be the same as your update arguments ensures the update method is non-blocking. By default, CPU.

Returns

MetricsLambda, F-beta metric

Return type

MetricsLambda

Examples

For more information on how metric works with Engine, visit Attach Engine API.

from collections import OrderedDict

import torch
from torch import nn, optim

from ignite.engine import *
from ignite.handlers import *
from ignite.metrics import *
from ignite.metrics.regression import *
from ignite.utils import *

# create default evaluator for doctests

def eval_step(engine, batch):
    return batch

default_evaluator = Engine(eval_step)

# create default optimizer for doctests

param_tensor = torch.zeros([1], requires_grad=True)
default_optimizer = torch.optim.SGD([param_tensor], lr=0.1)

# create default trainer for doctests
# as handlers could be attached to the trainer,
# each test must define his own trainer using `.. testsetup:`

def get_default_trainer():

    def train_step(engine, batch):
        return batch

    return Engine(train_step)

# create default model for doctests

default_model = nn.Sequential(OrderedDict([
    ('base', nn.Linear(4, 2)),
    ('fc', nn.Linear(2, 1))
]))

manual_seed(666)

Binary case

P = Precision(average=False)
R = Recall(average=False)
metric = Fbeta(beta=1.0, precision=P, recall=R)
metric.attach(default_evaluator, "f-beta")
y_true = torch.tensor([1, 0, 1, 1, 0, 1])
y_pred = torch.tensor([1, 0, 1, 0, 1, 1])
state = default_evaluator.run([[y_pred, y_true]])
print(state.metrics["f-beta"])

0.7499...

Multiclass case

P = Precision(average=False)
R = Recall(average=False)
metric = Fbeta(beta=1.0, precision=P, recall=R)
metric.attach(default_evaluator, "f-beta")
y_true = torch.tensor([2, 0, 2, 1, 0, 1])
y_pred = torch.tensor([
    [0.0266, 0.1719, 0.3055],
    [0.6886, 0.3978, 0.8176],
    [0.9230, 0.0197, 0.8395],
    [0.1785, 0.2670, 0.6084],
    [0.8448, 0.7177, 0.7288],
    [0.7748, 0.9542, 0.8573],
])
state = default_evaluator.run([[y_pred, y_true]])
print(state.metrics["f-beta"])

0.5222...

F-beta can be computed for each class as done below:

P = Precision(average=False)
R = Recall(average=False)
metric = Fbeta(beta=1.0, average=False, precision=P, recall=R)
metric.attach(default_evaluator, "f-beta")
y_true = torch.tensor([2, 0, 2, 1, 0, 1])
y_pred = torch.tensor([
    [0.0266, 0.1719, 0.3055],
    [0.6886, 0.3978, 0.8176],
    [0.9230, 0.0197, 0.8395],
    [0.1785, 0.2670, 0.6084],
    [0.8448, 0.7177, 0.7288],
    [0.7748, 0.9542, 0.8573],
])
state = default_evaluator.run([[y_pred, y_true]])
print(state.metrics["f-beta"])

tensor([0.5000, 0.6667, 0.4000], dtype=torch.float64)

The elements of y and y_pred should have 0 or 1 values. Thresholding of predictions can be done as below:

def thresholded_output_transform(output):
    y_pred, y = output
    y_pred = torch.round(y_pred)
    return y_pred, y

P = Precision(average=False, output_transform=thresholded_output_transform)
R = Recall(average=False, output_transform=thresholded_output_transform)
metric = Fbeta(beta=1.0, precision=P, recall=R)
metric.attach(default_evaluator, "f-beta")
y_true = torch.tensor([1, 0, 1, 1, 0, 1])
y_pred = torch.tensor([0.6, 0.2, 0.9, 0.4, 0.7, 0.65])
state = default_evaluator.run([[y_pred, y_true]])
print(state.metrics["f-beta"])

0.7499...