Add downsampling pipeline

moabb/pipelines/resample.py

@@ -0,0 +1,20 @@
+from scipy.signal import resample
+from sklearn.base import BaseEstimator, TransformerMixin
+
+
+"""
+Implements Sakhavi 2018
+(https://ieeexplore.ieee.org/document/8310961)
+section III, sub-section B, item 4.
+"""
+class Resample(TransformerMixin, BaseEstimator):
+    def __init__(self, old_fs=250, new_fs=10):
+        self.old_fs = old_fs
+        self.new_fs = new_fs
+
+    def fit(self, X, y):
+        return self
+
+    def transform(self, X):
+        n_samples_new = round( X.shape[2] * self.new_fs / self.old_fs )
+        return resample(X, n_samples_new, axis=2)