I assume you want to output the sinusoid values to an "analog output" (PWM) pin.
Take a look at MATLAB Support Package for Arduino. It allows you to send commands from MATLAB to Arduino, e.g.
a = arduino('COM9');
a.pinMode(13,'output'); % digital output
a.pinMode(9,'output'); % "analog output" (PWM)
% output the digital value (0 or 1) to pin 13
a.digitalWrite(13, 0)
% ouptput value on digital (pwm) pin 5
a.analogWrite(9, 120)
(The above code is from examples/example_io.m in the support package).