Having difficult time trying to plot a simple trajecory

[mesa]

Hello all, I am trying to plot a simple trajectory in MATlab. Here is the code I wrote,

v0 = 100;
theta = pi/4;
t=0:0.1:20;
horizontal(t)=t.*v0.*cos(theta)
vertical(t)=t.*v0.*sin(theta)-4.905.*t.^2
%teacher gone missing, again, ARRRGGHHH!
title('Ballistic Trajectory of a Projectile'), xlabel('horizontal distance, m'), ylabel('vertical distance, m')
plot (t,horizontal(t))

I am getting this error,

"Subscript indices must either be real positive integers or logicals."

If I input individual values for 't' it produces the correct results up until the vertical distance reaches it's 'maximum' but do not know why?

 

[SteamKing]

If 'horizontal (t)' and 'vertical (t)' are supposed to be arrays rather than functions of 't', then the error message would make sense.

To keep Matlab happy, why don't you use a dummy array index variable 'i' instead of t. Start with i = 1 and t = 0.0, and then t = (i - 1)*0.1

 

[jbunniii]

Just don't make the all too common error of redefining $i$ if your code uses complex numbers.

 

[mesa]

If 'horizontal (t)' and 'vertical (t)' are supposed to be arrays rather than functions of 't', then the error message would make sense.

To keep Matlab happy, why don't you use a dummy array index variable 'i' instead of t. Start with i = 1 and t = 0.0, and then t = (i - 1)*0.1

I'm new to Matlab so I am not sure what you mean by 'dummy array index variable' (this is not in my book). I do believe I see what you are getting at but we have been using,
t=0:0.1:20
and the lecturer is a jerk so anything outside what we go over, "...will result in a zero!" (has it plastered everywhere on the assignment).

Anyway, it isn't working for this plot so... :P

 

[mesa]

Got it, :P
This is a fickle program, grrrrrr

 

[mesa]

Got it, :P
This is a fickle program, grrrrrr

I take that back, this is a wonderful program.

 

[Bill Simpson]

and the lecturer is a jerk so anything outside what we go over, "...will result in a zero!" (has it plastered everywhere on the assignment).

That is perhaps because so many students use the internet to get their programming assignments done for them :)

 

[mesa]

That is perhaps because so many students use the internet to get their programming assignments done for them :)

That could be the reasoning behind these criteria although it seems most students in this class genuinely want to know how to write code.

A big part of the problem seems to be a Professor buried under departmental expectations that are unreasonable for a 1 credit hour course so with this new insight in mind I rescind my earlier comment about the lecturer; it is the department heads who are the jerks :)