Tutorial 2: Using multiple datasets

We extend the previous example to a case where we want to analyze the score of a classifier with three different MI datasets instead of just one. As before, we begin by importing all relevant libraries.

# Authors: Pedro L. C. Rodrigues, Sylvain Chevallier
#
# https://github.com/plcrodrigues/Workshop-MOABB-BCI-Graz-2019

import warnings

import matplotlib.pyplot as plt
import mne
import seaborn as sns
from mne.decoding import CSP
from sklearn.discriminant_analysis import LinearDiscriminantAnalysis as LDA
from sklearn.pipeline import make_pipeline

import moabb
from moabb.datasets import BNCI2014_001, Zhou2016
from moabb.evaluations import WithinSessionEvaluation
from moabb.paradigms import LeftRightImagery


moabb.set_log_level("info")
mne.set_log_level("CRITICAL")
warnings.filterwarnings("ignore")

/home/runner/work/moabb/moabb/.venv/lib/python3.11/site-packages/optuna/integration/sklearn.py:14: FutureWarning: `optuna.integration.sklearn` has been deprecated in v4.9.0. This feature will be removed in v6.0.0. See https://github.com/optuna/optuna/releases/tag/v4.9.0. Use `optuna_integration.sklearn` instead.
  optuna_warn(f"{msg} Use `optuna_integration.sklearn` instead.", FutureWarning)

Initializing Datasets

We instantiate the two different datasets that follow the MI paradigm (with left-hand/right-hand classes) but were recorded with different number of electrodes, different number of trials, etc.

datasets = [Zhou2016(), BNCI2014_001()]
subj = [1, 2, 3]
for d in datasets:
    d.subject_list = subj

The following lines go exactly as in the previous example, where we end up obtaining a pandas dataframe containing the results of the evaluation. We could set overwrite to False to cache the results, avoiding to restart all the evaluation from scratch if a problem occurs.

paradigm = LeftRightImagery()
evaluation = WithinSessionEvaluation(
    paradigm=paradigm, datasets=datasets, overwrite=False
)
pipeline = make_pipeline(CSP(n_components=8), LDA())
results = evaluation.process({"csp+lda": pipeline})

[codecarbon WARNING @ 23:35:37] Multiple instances of codecarbon are allowed to run at the same time.
2026-07-14 23:37:59,720 INFO MainThread moabb.evaluations.base csp+lda | Zhou2016 | 3 | 2: Score 0.994
2026-07-14 23:37:59,720 INFO MainThread moabb.evaluations.base csp+lda | Zhou2016 | 3 | 1: Score 0.982
2026-07-14 23:37:59,720 INFO MainThread moabb.evaluations.base csp+lda | Zhou2016 | 3 | 0: Score 0.952
2026-07-14 23:37:59,720 INFO MainThread moabb.evaluations.base csp+lda | Zhou2016 | 1 | 0: Score 0.853
2026-07-14 23:37:59,720 INFO MainThread moabb.evaluations.base csp+lda | Zhou2016 | 1 | 1: Score 0.906
2026-07-14 23:37:59,721 INFO MainThread moabb.evaluations.base csp+lda | Zhou2016 | 1 | 2: Score 0.948
2026-07-14 23:37:59,721 INFO MainThread moabb.evaluations.base csp+lda | Zhou2016 | 2 | 0: Score 0.910
2026-07-14 23:37:59,721 INFO MainThread moabb.evaluations.base csp+lda | Zhou2016 | 2 | 2: Score 0.906
2026-07-14 23:37:59,721 INFO MainThread moabb.evaluations.base csp+lda | Zhou2016 | 2 | 1: Score 0.760

Plotting Results

We plot the results using the seaborn library. Note how easy it is to plot the results from the three datasets with just one line.

results["subj"] = [str(resi).zfill(2) for resi in results["subject"]]
g = sns.catplot(
    kind="bar",
    x="score",
    y="subj",
    col="dataset",
    data=results,
    orient="h",
    palette="viridis",
)
plt.show()

2026-07-14 23:37:59,841 INFO MainThread matplotlib.category Using categorical units to plot a list of strings that are all parsable as floats or dates. If these strings should be plotted as numbers, cast to the appropriate data type before plotting.
2026-07-14 23:37:59,845 INFO MainThread matplotlib.category Using categorical units to plot a list of strings that are all parsable as floats or dates. If these strings should be plotted as numbers, cast to the appropriate data type before plotting.