Fixes #11: Add FFT/STFT and spectrogram visualization

src/signal_processing_toolkit/spectral.py

@@ -0,0 +1,22 @@
+import matplotlib.pyplot as plt
+import numpy as np
+import scipy.signal as signal
+
+
+def compute_fft(data, fs):
+    """Compute the Fast Fourier Transform of a 1D signal."""
+    n = len(data)
+    yf = np.fft.fft(data)
+    xf = np.fft.fftfreq(n, 1 / fs)
+    return xf[: n // 2], 2.0 / n * np.abs(yf[: n // 2])
+
+
+def compute_stft(data, fs, nperseg=256):
+    """Compute the Short-Time Fourier Transform."""
+    f, t, zxx = signal.stft(data, fs, nperseg=nperseg)
+    return f, t, np.abs(zxx)
+
+
+def plot_spectrogram(f, t, sxx):
+    """Visualizes STFT output as a spectrogram."""
+    plt.pcolormesh(t, f, 10 * np.log10(sxx), shading="gouraud")