> ## Documentation Index
> Fetch the complete documentation index at: https://nixtla-old-docs.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.
# Optimization
***
source
### mlforecast\_objective
> ```text theme={null}
> mlforecast_objective
> (df:Union[pandas.core.frame.DataFrame,polars.datafr
> ame.frame.DataFrame], config_fn:Callable[[optuna.tr
> ial._trial.Trial],Dict[str,Any]], loss:Callable,
> model:sklearn.base.BaseEstimator,
> freq:Union[int,str], n_windows:int, h:int,
> step_size:Optional[int]=None,
> input_size:Optional[int]=None,
> refit:Union[bool,int]=False,
> id_col:str='unique_id', time_col:str='ds',
> target_col:str='y')
> ```
*optuna objective function for the MLForecast class*
| | **Type** | **Default** | **Details** |
| ----------- | ------------- | ----------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
| df | Union | | |
| config\_fn | Callable | | Function that takes an optuna trial and produces a configuration with the following keys:
- model\_params
- mlf\_init\_params
- mlf\_fit\_params |
| loss | Callable | | Function that takes the validation and train dataframes and produces a float. |
| model | BaseEstimator | | scikit-learn compatible model to be trained |
| freq | Union | | pandas’ or polars’ offset alias or integer denoting the frequency of the series. |
| n\_windows | int | | Number of windows to evaluate. |
| h | int | | Forecast horizon. |
| step\_size | Optional | None | Step size between each cross validation window. If None it will be equal to `h`. |
| input\_size | Optional | None | Maximum training samples per serie in each window. If None, will use an expanding window. |
| refit | Union | False | Retrain model for each cross validation window.
If False, the models are trained at the beginning and then used to predict each window.
If positive int, the models are retrained every `refit` windows. |
| id\_col | str | unique\_id | Column that identifies each serie. |
| time\_col | str | ds | Column that identifies each timestep, its values can be timestamps or integers. |
| target\_col | str | y | Column that contains the target. |
| **Returns** | **Callable** | | |
```python theme={null}
import lightgbm as lgb
from datasetsforecast.m4 import M4, M4Evaluation, M4Info
from utilsforecast.losses import smape
from mlforecast.lag_transforms import ExpandingMean, RollingMean
from mlforecast.target_transforms import Differences, LocalBoxCox, LocalStandardScaler
```
```python theme={null}
def train_valid_split(group):
df, *_ = M4.load(directory='data', group=group)
df['ds'] = df['ds'].astype('int')
horizon = M4Info[group].horizon
valid = df.groupby('unique_id').tail(horizon)
train = df.drop(valid.index)
return train, valid
```
```python theme={null}
h = M4Info['Weekly'].horizon
weekly_train, weekly_valid = train_valid_split('Weekly')
weekly_train['unique_id'] = weekly_train['unique_id'].astype('category')
weekly_valid['unique_id'] = weekly_valid['unique_id'].astype(weekly_train['unique_id'].dtype)
```
```python theme={null}
def config_fn(trial):
candidate_lags = [
[1],
[13],
[1, 13],
range(1, 33),
]
lag_idx = trial.suggest_categorical('lag_idx', range(len(candidate_lags)))
candidate_lag_tfms = [
{
1: [RollingMean(window_size=13)]
},
{
1: [RollingMean(window_size=13)],
13: [RollingMean(window_size=13)],
},
{
13: [RollingMean(window_size=13)],
},
{
4: [ExpandingMean(), RollingMean(window_size=4)],
8: [ExpandingMean(), RollingMean(window_size=4)],
}
]
lag_tfms_idx = trial.suggest_categorical('lag_tfms_idx', range(len(candidate_lag_tfms)))
candidate_targ_tfms = [
[Differences([1])],
[LocalBoxCox()],
[LocalStandardScaler()],
[LocalBoxCox(), Differences([1])],
[LocalBoxCox(), LocalStandardScaler()],
[LocalBoxCox(), Differences([1]), LocalStandardScaler()],
]
targ_tfms_idx = trial.suggest_categorical('targ_tfms_idx', range(len(candidate_targ_tfms)))
return {
'model_params': {
'learning_rate': 0.05,
'objective': 'l1',
'bagging_freq': 1,
'num_threads': 2,
'verbose': -1,
'force_col_wise': True,
'n_estimators': trial.suggest_int('n_estimators', 10, 1000, log=True),
'num_leaves': trial.suggest_int('num_leaves', 31, 1024, log=True),
'lambda_l1': trial.suggest_float('lambda_l1', 0.01, 10, log=True),
'lambda_l2': trial.suggest_float('lambda_l2', 0.01, 10, log=True),
'bagging_fraction': trial.suggest_float('bagging_fraction', 0.75, 1.0),
'feature_fraction': trial.suggest_float('feature_fraction', 0.75, 1.0),
},
'mlf_init_params': {
'lags': candidate_lags[lag_idx],
'lag_transforms': candidate_lag_tfms[lag_tfms_idx],
'target_transforms': candidate_targ_tfms[targ_tfms_idx],
},
'mlf_fit_params': {
'static_features': ['unique_id'],
}
}
def loss(df, train_df):
return smape(df, models=['model'])['model'].mean()
```
```python theme={null}
optuna.logging.set_verbosity(optuna.logging.WARNING)
objective = mlforecast_objective(
df=weekly_train,
config_fn=config_fn,
loss=loss,
model=lgb.LGBMRegressor(),
freq=1,
n_windows=2,
h=h,
)
study = optuna.create_study(
direction='minimize', sampler=optuna.samplers.TPESampler(seed=0)
)
study.optimize(objective, n_trials=2)
best_cfg = study.best_trial.user_attrs['config']
final_model = MLForecast(
models=[lgb.LGBMRegressor(**best_cfg['model_params'])],
freq=1,
**best_cfg['mlf_init_params'],
)
final_model.fit(weekly_train, **best_cfg['mlf_fit_params'])
preds = final_model.predict(h)
M4Evaluation.evaluate('data', 'Weekly', preds['LGBMRegressor'].values.reshape(-1, 13))
```
| | SMAPE | MASE | OWA |
| ------ | -------- | -------- | -------- |
| Weekly | 9.261538 | 2.614473 | 0.976158 |