new, faster version

examples/test_butter.jl

@@ -24,6 +24,7 @@ results = zeros(N)
 for i in 1:N
     results[i] = apply_filter(butter, measurements[i], buffer, i)
 end
+@time apply_filter(butter, measurements[N], buffer, N)
 
 # Plot the step response
 p = plot((1:N)*dt, [measurements, results]; xlabel="Time (s)", ylabel="Amplitude", 

examples/test_butter2.jl

@@ -0,0 +1,50 @@
+using DiscreteFilters, ControlPlots, DSP, ControlSystemsBase, Printf, LaTeXStrings
+include("plotting.jl")
+
+function create_filter2(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
+function apply_filter2(butterF, measurement, index)
+    results = zeros(1)
+    measurements = ones(1) * measurement
+    @views filt!(results[1:1], butterF, measurements)
+    return results[1]
+end
+
+# Define the cut-off frequency in Hz
+cut_off_freq = 2.0
+
+# Define the sampling and simulation time in seconds
+dt = 0.05
+sim_time = 4.0
+N = Int(sim_time / dt)
+
+# Design the filter
+butter = create_filter2(cut_off_freq; order=4, dt)
+
+# Create an array of measurements (step signal)
+measurements = zeros(N)
+for i in Int(N/2):N
+    measurements[i] = 1.0
+end
+
+# apply the filter
+results = zeros(N)
+tfilter = DSP.Filters.DF2TFilter(butter)
+for i in 1:N
+    results[i] = apply_filter2(tfilter, measurements[i], i)
+end
+@time apply_filter2(tfilter, measurements[N], N)
+
+# Plot the step response
+p = plot((1:N)*dt, [measurements, results]; xlabel="Time (s)", ylabel="Amplitude", 
+         labels=["Input" "Output"], fig="Forth order Butterworth Filter")
+display(p)
+
+# Plot the frequency response
+bo = tf(butter, dt)
+bode_plot(bo; hz=true, from=0.5, to=1.5, title="4th order Butterworth Filter")