バターワース フィルターを適用する必要があります。カットオフ周波数を証明するために、右の画像に示すように、残差とカットオフ周波数をプロットしたいと思います。
残差は、左の図に示す式を使用して計算されます。
2 次のローパス バタワース フィルターを適用したいと考えています。私のサンプル周波数は 40 Hz です。
help butter読み取りの使用:
「カットオフ周波数 Wn は 0.0 < Wn < 1.0 でなければならず、1.0 はサンプルレートの半分に対応します」。
これは私のコードですx。フィルタリングされていないデータは次のとおりです。
x = 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wc = 0.001:0.001:1 % <----- !!!
R = zeros(1, length(wc)-1);
for nn = 1:length(wc)-1
[B,A] = butter(2,wc(nn));
xprime = filtfilt(B,A,x);
R(1,nn) = sqrt(1/length(x)*(sum(abs(x-xprime).^2)))
end
plot(wc(1:end-1)*20,R) % <------ !!!!
そして、私はこれを得ました：
しかし、これは私には正しくないようです。私は何を間違っていますか？
