first commit

LICENSE

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+            DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
+                    Version 2, December 2004
+
+ Copyright (C) 2004 Sam Hocevar <sam@hocevar.net>
+
+ Everyone is permitted to copy and distribute verbatim or modified
+ copies of this license document, and changing it is allowed as long
+ as the name is changed.
+
+            DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
+   TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
+
+  0. You just DO WHAT THE FUCK YOU WANT TO.
+

README.md

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+# Reverse Goertzel
+
+Code using the Goertzel algorithm in reverse.

reverse_goertzel.py

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+import math
+import matplotlib.pyplot as plt
+import numpy as np
+
+def goertzel_sinusoid(freq, duration, sample_rate, amplitude):
+    n = int(duration * sample_rate)
+    omega = (2.0 * math.pi * freq) / sample_rate
+    coeff = 2.0 * math.cos(omega)
+    
+    # Initialize state variables
+    q1 = 1.0
+    q2 = 1.0
+    result = []
+    
+    for i in range(n):
+        sample = coeff * q1 - q2
+        q2 = q1
+        q1 = sample
+        result.append(sample * amplitude)
+    
+    return result
+
+def sinusoid(n, cycles=1):
+    result = []
+    for i in range(1, n+1):
+        sample = math.cos(2.0 * cycles * math.pi * (i/n))
+        result.append(sample)
+    return result
+
+def main():
+    cycles = 2
+    signal = goertzel_sinusoid(cycles, 1, 1024, 1)
+    reference = np.array(sinusoid(1024, cycles))
+    error = reference - signal
+    print("max error:", error.max())
+    x = np.array(range(0, 1024))
+    plt.plot(x, signal)
+    plt.plot(x, reference)
+    plt.plot(x, error)
+    #plt.plot(x, error*1000/3)
+    plt.show()
+
+if __name__ == "__main__":
+    main()