add sawtooth generator function

src/generate_sawtooth.m

@@ -0,0 +1,38 @@
+function x = generate_sawtooth(amplitude, frequency, phase, fs, duration, duty)
+% generate_sawtooth: returns a matrix of sampled sawtooth wave
+
+% CONTRIBUTORS:
+% Ben Zhang: Function author
+% Arthur Lu: Format author
+
+% DOCUMENTATION:
+% phase shift is in number of periods
+% fs is the sampling frequency: how many sample points per second
+% duration is time in seconds
+% duty is a number between 0 and 1 
+    %duty does not apply for sawtooth wave
+
+    % 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
+    period = 1 / frequency; % period of the wave
+    
+    % initialize a one dimensional zero matrix to be populated
+    x = zeros(1, n);
+    
+    % populate the matrix
+    for i = 1:n
+        t = i * dt; % time of the i'th sample
+        st = mod(frequency * t - phase, 1); % Progression through cycle
+        
+        slope = 2 * amplitude / period; % the incline slope from start to amplitude
+        %part before the straght vertical line
+        if(st < period /2)
+            x(i) = slope * st;
+        
+        %part after the straght vertical line
+        else
+            x(i) = slope * st - amplitude;
+        
+    end
+end