Clojure(JVMで動くLISP系）でJavaの数値計算ライブラリApache Commons Mathを使う(3) 高速フーリエ変換（FFT）を実行してJFreeChartでプロットする。

今回はこの移植。

 Javaの数値計算ライブラリApache Commons Mathを使う(3) 高速フーリエ変換（FFT）を実行してJFreeChartでプロットする。

コードはこんな感じで。

(ns mini.fft

  (:import [org.apache.commons.math3.complex Complex]

           [org.apache.commons.math3.transform FastFourierTransformer DftNormalization TransformType]

           [org.jfree.data.xy XYSeriesCollection XYSeries]

           [org.jfree.chart ChartFactory  ChartPanel]

           [org.jfree.chart.renderer.xy XYLineAndShapeRenderer]

           [javax.swing JFrame]))

(def n 256)

(def t (make-array Double/TYPE n))

(def y (make-array Double/TYPE n))

(def f (make-array Double/TYPE n))

(def fft (FastFourierTransformer. DftNormalization/STANDARD))

(dotimes [i n]

  (aset t i (double i))

  (aset y i (Math/sin (aget t i)))

  (aset f i (- (/ (double i) (double n)) 0.5)))

(def result (.transform fft y TransformType/FORWARD))

(def resultShift (make-array Complex n))

(dotimes [i (/ n 2)]

  (aset resultShift i (aget result (+ i (/ n 2))))

  (aset resultShift (+ i (/ n 2)) (aget result i)))

(defn create-dataset []

  (let [series  (XYSeries. "Real Part")

        series2 (XYSeries. "Imaginary Part")]

    (dotimes [i n]

      (.add series (aget f i) (.getReal (aget resultShift i)))

      (.add series2 (aget f i) (.getImaginary (aget resultShift i))) )

      (doto (XYSeriesCollection.)

        (.addSeries series)

        (.addSeries series2)

        )))

(defn create-chart [dataset]

  (ChartFactory/createXYLineChart

   "Fast Fourier Transform"

   "frequency"

   "result"

   dataset))

(defn display-chart [chart]

  (let [frame (JFrame. "FFT")

        plot (.getXYPlot chart)

        renderer (XYLineAndShapeRenderer.)

        chart-panel (ChartPanel. chart)]

    (.setSeriesShapesVisible renderer 0 false) ; 線だけ

    (.setSeriesShapesVisible renderer 1 false) ; 線だけ

    (.setRenderer plot renderer)

    (doto frame

      (.add chart-panel)

      (.pack)

      (.setVisible true))))

(defn -main []

  (let [dataset (create-dataset)

        chart (create-chart dataset)]

    (display-chart chart)))

(-main)

結果はこちら。