Intro to OpenSim API in Matlab. To configure Matlab to access OpenSim, visit https://simtk-confluence.stanford.edu/display/OpenSim/Scripting+with+Matlab

IntroOpenSimAPI.m

import org.opensim.modeling.*;

% Build a model.
model = Model();
body = Body('body', 1.0, Vec3(0), Inertia(0));
body.attachGeometry(Sphere(0.1));
model.addBody(body);

joint = SliderJoint('joint', model.getGround(), body);
coord = joint.updCoordinate();
coord.setName('translation');
model.addJoint(joint);

actuator = CoordinateActuator('translation');
actuator.setName('actuator');
model.addForce(actuator);

controller = PrescribedController();
% methodsview(controller);
controller.addActuator(actuator);
controller.prescribeControlForActuator('actuator', Sine());
model.addController(controller);

model.finalizeConnections();
model.print('pointmass.osim');

% Simulate a model.
model.setUseVisualizer(true);
initState = model.initSystem();
disp(initState.getY());
finalState = opensimSimulation.simulate(model, initState, 1.5);

% Analyze a simulation.
disp(coord.getValue(finalState));
model.realizePosition(finalState);
disp(model.calcMassCenterPosition(finalState));
model.realizeAcceleration(finalState);
disp(joint.calcReactionOnParentExpressedInGround(finalState));

% Inspect and modify a model.
clear all;
model = Model('pointmass.osim');
body = model.updBodySet().get('body');
body.setMass(2 * body.getMass());
force = model.updForceSet().get('actuator');
disp(class(force));
actuator = CoordinateActuator.safeDownCast(force);
disp(class(actuator));
actuator.setOptimalForce(4 * actuator.getOptimalForce());

% Simulate the modified model.
initState = model.initSystem();
disp(initState.getY());
finalState = opensimSimulation.simulate(model, initState, 1.5);
disp(model.getCoordinateSet().get('translation').getValue(finalState));