Swift: Obtaining Plot Data

[Tauf]

I want to extract the data used to plot my audio file, so I can plot them later with Excel in my computer. In other words, EZAudioPlot has some x and y-componet to plot a buffering wave, I want to extract those in an array and plot them with amplitude on y-axis and time on x-axis.

Here is my code, I don't know how to use getwaveformdata():

       func setupPlot() {
        let plot = AKNodeOutputPlot(microphone, frame: audioInputPlot.bounds)

        plot.plotType = .buffer
        plot.shouldFill = false
        plot.shouldMirror = false
        plot.shouldCenterYAxis = true
        plot.color = Gold

        }
        let documentsUrl = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first!

        let audioFilePath = documentsUrl.appendingPathComponent("AudioFile-2017-03-04-13-38-45.m4a")

        let audioFile = EZAudioFile(url: URL(fileURLWithPath: audioFilePath.path))
        let waveformData = audioFile!.getWaveformData()

        plot.updateBuffer(waveformData?.buffers[0], withBufferSize: (waveformData?.bufferSize)!)
        print(waveformData ?? "no WaveFormData")