add test5

pasada-lib/include/iir_filter.h

@@ -42,7 +42,18 @@ protected:
     Filt y;
     Filt x;
 public:
+    /**
+     * Create IIR filter from coefficients 'b' and 'a' (numerator and denominator polynomial coefficients).
+     */
     IirFilter(std::vector<double> b, std::vector<double> a);
+
+    /**
+     * Create Butterworth lowpass filter.
+     * @param N order of Butterworth filter
+     * @param fc cutoff frequency in Hz
+     * @param fs sampling rate in Hz
+     */
+    IirFilter(int N, double fc, double fs);
     double filter(double val);
 };