add wave genration functions

src/generate_square.m

@@ -0,0 +1,20 @@
+function x = generate_square(amplitude, frequency, phase, fs, duration, duty)
+%GENERATE_SINE:Arthur Lu returns a matrix of sampled sine wave, where the
+%phase shift is in number of periods
+    x = zeros(1, fs * duration);
+    A = amplitude;
+    f = frequency;
+    p = phase;
+    n = fs * duration;
+    dt = 1 / fs;
+    for i = 1:n
+        t = i * dt;
+        st = mod(f * t - p, 1);
+        if(st < duty)
+            x(i) = A;
+        else
+            x(i) = -A;
+        end
+    end
+end
+