Added first draft of generating heart monitor wave

src/generate_heart_monitor.m

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+function x = generate_heart_monitor(amplitude, frequency, phase, fs, duration, duty)
+% GENERATE_SINE: returns a matrix of sampled heart monitor wave
+
+% CONTRIBUTORS:
+% Alex Nguyen: Original 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 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; % time at the i'th sample
+        st = mod(frequency * t - phase, 1);
+
+        if (duty-0.1 < st && st < duty)
+            slope = amplitude / duty;
+            intercept = -0.5 * amplitude;
+            x(i) = slope * st + intercept;
+        elseif (duty < st && st < duty+0.1) 
+            slope = -amplitude / duty;
+            intercept = amplitude * (duty/(1-duty) + 0.5);
+            x(i) = slope * st + intercept;
+        else
+            x(i) = 0;
+    end
+end
+