# Cubic poly trajectory function

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Odesanmi Gbenga Abiodun on 4 Aug 2022
Commented: Sam Chak on 5 Aug 2022
I am using matlab2018b and I can't use cubicpolytraj function. please what's the alternative function I can use. Thanks

Sam Chak on 4 Aug 2022
One practical alternative and a mearning way to learn how to generate 3rd-order trajectories is to mathematically derive the 3rd-order polynomical function yourself:  or to use the formula directly: Say you to get from Point A to Point B in 4 seconds:  t = linspace(0, 4, 401);
A = [2, 3];
B = [5, 7];
x = 2 + (3*(t/4).^2 - 2*(t/4).^3)*(5 - 2);
y = 3 + (3*(t/4).^2 - 2*(t/4).^3)*(7 - 3);
plot(t, [x; y]), ylim([1 8]), grid on,
xlabel('t'), ylabel('Positions'), legend('X-positions','Y-positions') Or get a 3rd-party MATLAB code from File Exchange.
plot([A(1), B(1)], [A(2), B(2)], 'o'), hold on
plot(x, y), xlim([1 6]), ylim([2 8]), grid on,
xlabel('x'), ylabel('y'), ##### 2 CommentsShowHide 1 older comment
Sam Chak on 5 Aug 2022
You are welcome, @Odesanmi Gbenga Abiodun. Yes, you can apply exactly the same formula to find the 4 sets of 3rd-order polynomial functions for the five (5) waypoints in 3D {x, y, z} coordinates.
If you find the formula, example, MATLAB code helpful, please consider accepting ✔ and voting 👍 the Answer. Thanks!