Merge pull request #7 from ltcptgeneral/improve_comments

Added additional comments for wave generation functions

src/generate_sine.m

@@ -1,15 +1,28 @@
 function x = generate_sine(amplitude, frequency, phase, fs, duration, duty)
-%GENERATE_SINE:Arthur Lu returns a matrix of sampled sine wave, where the
+% GENERATE_SINE: returns a matrix of sampled sine wave
-%phase shift is in number of periods
+
-    x = zeros(1, fs * duration);
+% CONTRIBUTORS:
-    A = amplitude;
+% Arthur Lu: Original author
-    f = frequency;
+% Benjamin Liou: refactoring and annotations
-    p = phase;
+
-    n = fs * duration;
+% DOCUMENTATION:
-    dt = 1 / fs;
+% phase shift is in number of periods
+% fs is the sampling frequency: how many sample points per second
+% duration is time in seconds
+% duty does not apply for sinusoids
+   
+
+    % initialize local variables from input arguments
+    n = fs * duration; % number of samples (length of matrix)
+    dt = 1 / fs; % sampling period: time between two sample points
+    
+    % initialize a one dimensional zero matrix to be populated
+    x = zeros(1, n);
+    
+    % populate the matrix
     for i = 1:n
-        t = i * dt;
+        t = i * dt; % time at the i'th sample
-        x(i) = A * sin(2 * pi * f * t - p);
+        x(i) = amplitude * sin(2 * pi * frequency * t - phase);
     end
 end
 

src/generate_square.m

@@ -1,19 +1,40 @@
 function x = generate_square(amplitude, frequency, phase, fs, duration, duty)
-%GENERATE_SINE:Arthur Lu returns a matrix of sampled sine wave, where the
+% GENERATE_SQUARE: returns a matrix of sampled square wave
-%phase shift is in number of periods
+
-    x = zeros(1, fs * duration);
+% CONTRIBUTORS:
-    A = amplitude;
+% Arthur Lu: Original author
-    f = frequency;
+% Benjamin Liou: refactoring and annotations
-    p = phase;
+
-    n = fs * duration;
+% DOCUMENTATION:
-    dt = 1 / fs;
+% phase shift is in number of periods
+% fs is the sampling frequency: how many sample points per second
+% duration is time in seconds
+% duty cycle should be a number between 0 and 1.
+    % duty of 0 or less would return -amplitude for all sample points
+    % duty of 0.25 would return +amplitude for first quarter of each cycle
+        % then return -amplitude for the remaining three-fourths
+    % duty of 1 would return all +amplitude
+
+
+% initialize local variables from input arguments
+    n = fs * duration; % number of samples (length of matrix)
+    dt = 1 / fs; % sampling period: time between two sample points
+    
+    % initialize a one dimensional zero matrix to be populated
+    x = zeros(1, n);
+    
+    % populate the matrix
     for i = 1:n
-        t = i * dt;
+        t = i * dt; % time at the i'th sample
-        st = mod(f * t - p, 1);
+        
+        % periodic ramp from 0 to 1
+        % progression through a cycle
+        st = mod(frequency * t - phase, 1);
+        
         if(st < duty)
-            x(i) = A;
+            x(i) = amplitude;
         else
-            x(i) = -A;
+            x(i) = -amplitude;
         end
     end
 end

src/generate_triangle.m

@@ -1,19 +1,43 @@
 function x = generate_triangle(amplitude, frequency, phase, fs, duration, duty)
-%GENERATE_SINE:Arthur Lu returns a matrix of sampled sine wave, where the
+% GENERATE_TRIANGLE: returns a matrix of sampled square wave
-%phase shift is in number of periods
+
-    x = zeros(1, fs * duration);
+% CONTRIBUTORS:
-    A = amplitude;
+% Arthur Lu: Original author
-    f = frequency;
+% Benjamin Liou: refactoring and annotations
-    p = phase;
+
-    n = fs * duration;
+% DOCUMENTATION:
-    dt = 1 / fs;
+% phase shift is in number of periods
+% fs is the sampling frequency: how many sample points per second
+% duration is time in seconds
+% duty cycle should be a number between 0 and 1.
+    % duty of 0.25 would have positive slope for first quarter of each cycle
+        % then have negative slope for the remaining three-fourths
+
+
+
+% initialize local variables from input arguments
+    n = fs * duration; % number of samples (length of matrix)
+    dt = 1 / fs; % sampling period: time between two sample points
+    
+    % initialize a one dimensional zero matrix to be populated
+    x = zeros(1, n);
+    
+    % populate the matrix
     for i = 1:n
         t = i * dt;
-        st = mod(f * t - p, 1);
+        
+        % periodic ramp from 0 to 1
+        % progression through a cycle
+        st = mod(frequency * t - phase, 1);
+        
         if(st < duty)
-            x(i) = A*(1/duty * st - 0.5);
+            slope = amplitude / duty;
+            intercept = -0.5 * amplitude;
+            x(i) = slope * st + intercept;
         else
-            x(i) = A*(-(1/(1-duty))*st + (duty/(1-duty)) + 1 - 0.5);
+            slope = -amplitude / (1 - duty);
+            intercept = amplitude*( duty/(1-duty) + 0.5);
+            x(i) = slope * st + intercept;
         end
     end
 end