add chebychef filter

examples/test_lowpass.jl

@@ -8,6 +8,10 @@ dt = 0.05
 sim_time = 4.0
 N = Int(sim_time / dt)
 
+# Design the filter
+butter = create_filter(cut_off_freq; order=4, dt)
+cheby1 = create_filter(cut_off_freq; order=4, type=:Cheby1, dt)
+
 # Create an array of measurements
 measurements = zeros(N)
 for i in Int(N/2):N
@@ -31,6 +35,13 @@ for i in 1:N
     results_butter[i] = apply_filter(butter, measurements[i], buffer, i)
 end
 
+# Apply the Cheby1 filter
+buffer = zeros(N)
+results_cheby1 = zeros(N)
+for i in 1:N
+    results_cheby1[i] = apply_filter(cheby1, measurements[i], buffer, i)
+end
+
 # Plot the results
-plot((1:N)*dt, [measurements, results, results_butter]; xlabel="Time (s)", ylabel="Amplitude", 
+plot((1:N)*dt, [measurements, results, results_butter, results_cheby1]; xlabel="Time (s)", ylabel="Amplitude", 
      fig="Exponential Moving Average and Butterworth Filters")

src/DiscreteFilters.jl

@@ -41,8 +41,12 @@ Design a Butterworth filter with the given cut-off frequency.
 - `order`: The order of the filter, optionally, default: 4
 - `dt`: The sampling time in seconds
 """
-function create_filter(cut_off_freq; order=4, dt)
-    Filters.digitalfilter(Filters.Lowpass(cut_off_freq; fs=1/dt), Filters.Butterworth(order))
+function create_filter(cut_off_freq; order=4, type=:Butter, dt)
+    if type == :Butter
+        return Filters.digitalfilter(Filters.Lowpass(cut_off_freq; fs=1/dt), Filters.Butterworth(order))
+    elseif type == :Cheby1
+        return Filters.digitalfilter(Filters.Lowpass(cut_off_freq; fs=1/dt), Filters.Chebyshev1(order, 0.01))
+    end
 end
 
 """