adds realtime spectrum plot using GR.jl

examples/spectrum.jl

@@ -0,0 +1,27 @@
+module SpectrumExample
+
+using GR, PortAudio, SampleTypes
+
+const N = 1024
+const stream = PortAudioStream(1, 1, bufsize=N)
+const buf = read(stream, N)
+const fmin = 0Hz
+const fmax = 10000Hz
+const fs = Float32[float(f) for f in domain(fft(buf)[fmin..fmax])]
+
+setwindow(fs[1], fs[end], 0, 100)
+setviewport(0.05, 0.95, 0.05, 0.95)
+setlinecolorind(218)
+setfillintstyle(1)
+setfillcolorind(208)
+setscale(GR.OPTION_X_LOG)
+
+while true
+    read!(stream, buf)
+    clearws()
+    fillrect(fs[1], fs[end], 0, 100)
+    polyline(fs, abs(fft(buf)[fmin..fmax]))
+    updatews()
+end
+
+end