Managing Accelerations - Sinusoidal Pattern

Hello everyone, I would like to get an advice about an issue I am struggling with.

I am using a 5 D.o.F. robotic manipulator that would replicate the trajectory made by a marker, which is recorded by a webcam, processed by Python and sent to the robot as G-Code lines via Python - LinuxCNC interface. 

The robot can follow the trajectory of the marker only if it moves at a constant speed, by setting a right feedrate. But what if the marker moves with accelerations? 

I would like to follow a sinusoidal pattern over time (so with accelerations and deceleration close to sinusoid maxima and minima), is there a method to do this in LinuxCNC and/or in Python? In other words, is there a method that allows me to make an acceleration or deceleration in certain G-Code lines?

Thanks in advance to everyone who could help me.