import math
from typing import Callable
from typing import cast
from typing import List
from typing import Optional
from typing import Tuple
from typing import Union
from optuna._experimental import experimental
from optuna.logging import get_logger
from optuna.study import Study
from optuna.trial import FrozenTrial
from optuna.trial import TrialState
from optuna.visualization._utils import _check_plot_args
from optuna.visualization.matplotlib._matplotlib_imports import _imports
from optuna.visualization.matplotlib._utils import _is_log_scale
from optuna.visualization.matplotlib._utils import _is_numerical
if _imports.is_successful():
from optuna.visualization.matplotlib._matplotlib_imports import Axes
from optuna.visualization.matplotlib._matplotlib_imports import Colormap
from optuna.visualization.matplotlib._matplotlib_imports import matplotlib
from optuna.visualization.matplotlib._matplotlib_imports import PathCollection
from optuna.visualization.matplotlib._matplotlib_imports import plt
_logger = get_logger(__name__)
[docs]@experimental("2.2.0")
def plot_slice(
study: Study,
params: Optional[List[str]] = None,
*,
target: Optional[Callable[[FrozenTrial], float]] = None,
target_name: str = "Objective Value",
) -> "Axes":
"""Plot the parameter relationship as slice plot in a study with Matplotlib.
.. seealso::
Please refer to :func:`optuna.visualization.plot_slice` for an example.
Example:
The following code snippet shows how to plot the parameter relationship as slice plot.
.. plot::
import optuna
def objective(trial):
x = trial.suggest_float("x", -100, 100)
y = trial.suggest_categorical("y", [-1, 0, 1])
return x ** 2 + y
sampler = optuna.samplers.TPESampler(seed=10)
study = optuna.create_study(sampler=sampler)
study.optimize(objective, n_trials=10)
optuna.visualization.matplotlib.plot_slice(study, params=["x", "y"])
Args:
study:
A :class:`~optuna.study.Study` object whose trials are plotted for their target values.
params:
Parameter list to visualize. The default is all parameters.
target:
A function to specify the value to display. If it is :obj:`None` and ``study`` is being
used for single-objective optimization, the objective values are plotted.
.. note::
Specify this argument if ``study`` is being used for multi-objective optimization.
target_name:
Target's name to display on the axis label.
Returns:
A :class:`matplotlib.axes.Axes` object.
"""
_imports.check()
_check_plot_args(study, target, target_name)
return _get_slice_plot(study, params, target, target_name)
def _get_slice_plot(
study: Study,
params: Optional[List[str]] = None,
target: Optional[Callable[[FrozenTrial], float]] = None,
target_name: str = "Objective Value",
) -> "Axes":
# Calculate basic numbers for plotting.
trials = [trial for trial in study.trials if trial.state == TrialState.COMPLETE]
if len(trials) == 0:
_logger.warning("Your study does not have any completed trials.")
_, ax = plt.subplots()
return ax
all_params = {p_name for t in trials for p_name in t.params.keys()}
if params is None:
sorted_params = sorted(all_params)
else:
for input_p_name in params:
if input_p_name not in all_params:
raise ValueError("Parameter {} does not exist in your study.".format(input_p_name))
sorted_params = sorted(set(params))
n_params = len(sorted_params)
# Set up the graph style.
cmap = plt.get_cmap("Blues")
padding_ratio = 0.05
plt.style.use("ggplot") # Use ggplot style sheet for similar outputs to plotly.
# Prepare data.
if target is None:
obj_values = [cast(float, t.value) for t in trials]
else:
obj_values = [target(t) for t in trials]
if n_params == 1:
# Set up the graph style.
fig, axs = plt.subplots()
axs.set_title("Slice Plot")
# Draw a scatter plot.
sc = _generate_slice_subplot(
trials, sorted_params[0], axs, cmap, padding_ratio, obj_values, target_name
)
else:
# Set up the graph style.
min_figwidth = matplotlib.rcParams["figure.figsize"][0] / 2
fighight = matplotlib.rcParams["figure.figsize"][1]
# Ensure that each subplot has a minimum width without relying on auto-sizing.
fig, axs = plt.subplots(
1, n_params, sharey=True, figsize=(min_figwidth * n_params, fighight)
)
fig.suptitle("Slice Plot")
# Draw scatter plots.
for i, param in enumerate(sorted_params):
ax = axs[i]
sc = _generate_slice_subplot(
trials, param, ax, cmap, padding_ratio, obj_values, target_name
)
axcb = fig.colorbar(sc, ax=axs)
axcb.set_label("Trial")
return axs
def _generate_slice_subplot(
trials: List[FrozenTrial],
param: str,
ax: "Axes",
cmap: "Colormap",
padding_ratio: float,
obj_values: List[Union[int, float]],
target_name: str,
) -> "PathCollection":
x_values = []
y_values = []
trial_numbers = []
scale = None
for t, obj_v in zip(trials, obj_values):
if param in t.params:
x_values.append(t.params[param])
y_values.append(obj_v)
trial_numbers.append(t.number)
ax.set(xlabel=param, ylabel=target_name)
if _is_log_scale(trials, param):
ax.set_xscale("log")
scale = "log"
elif not _is_numerical(trials, param):
x_values = [str(x) for x in x_values]
scale = "categorical"
xlim = _calc_lim_with_padding(x_values, padding_ratio, scale)
ax.set_xlim(xlim[0], xlim[1])
sc = ax.scatter(x_values, y_values, c=trial_numbers, cmap=cmap, edgecolors="grey")
ax.label_outer()
return sc
def _calc_lim_with_padding(
values: List[Union[int, float]], padding_ratio: float, scale: Optional[str] = None
) -> Tuple[Union[int, float], Union[int, float]]:
value_max = max(values)
value_min = min(values)
if scale == "log":
padding = (math.log10(value_max) - math.log10(value_min)) * padding_ratio
return (
math.pow(10, math.log10(value_min) - padding),
math.pow(10, math.log10(value_max) + padding),
)
elif scale == "categorical":
width = len(set(values)) - 1
padding = width * padding_ratio
return -padding, width + padding
else:
padding = (value_max - value_min) * padding_ratio
return value_min - padding, value_max + padding