You need to specify the multiplication operators (*). I added element-wise exponentiation. You also need to save your function to its own file as height.m on your MATLAB user path.
This is not as efficient as it could be, however it will get you started:
function [y]=height(t)
if (t<0)
y=0;
elseif (t<15)
y=38.1454*t+0.13743*t.^3;
elseif (t<33) & (t>=15)
y=1036+103.909*(t-15)+6.18425*(t-15).^2-0.428*(t-15).^3;
elseif (t>33)
y=2900-62.468*(t-33)-16.9274*(t-33).^2+0.41796*(t-33).^3;
end
end
t = linspace(0, 50, 50);
for k1 = 1:numel(t)
h(k1) = height(t(k1));
end
figure
plot(t, h)
grid
Experiment to get the result you want.
