My professor is driving me crazy.

So i have the following exercise i have to use this formula with a t that starts at 0 and goes all the way to 50 with a step of 5. calculate and present in a table. i did this,

step=5
tmax=50 
X = [0:step:tmax;10*(1-exp(-0.2*(0:step:tmax)))];

and he said to me that the formula is not correct. I have been staring at it for an hour and it's driving me nuts. Can someone please explain to me were i went wrong and why? :/

formula

Answer 1

[Image Analyst]

I'd bet it's because you, for some reason, decided to change the name of the variable from u, which your professor wanted, to X. And you didn't even use t AT ALL !

Why did you do that? Give him what he wants.

[James Tursa]

... omg ... you might be right!

[John D'Errico]

I think indeed the animalyst has hit on the answer here.

[Athanasios Naminsenoiazi]

Here is the full code, X is just temporary

tmax = 50;
step = 5;

X = [0:step:tmax;10*(1-exp(-0.2*(0:step:tmax)))];

t = [];
ut = [];

for i=1:2
    for j=1:11
        if i == 1
            t = [t;X(i,j)];
        elseif i == 2
            ut = [ut;X(i,j)];
        end
    end
end

T = table(t,ut);
T

Plus i never used t at all because this way is way more elegant that having a loop...

[Image Analyst]

Did he ask for a table? If not, why did you make one?

This is what I'd do

t = 0 : 5 : 50;
u = 10 * (1 - exp(-0.2 * t));

Simply create vector t then use it to create the vector u that he wants.

From your original post, I don't see any need to use for loops, tables, variables called X or T, or even 2-D matrices. The two lines of code above should do it.

Answer 2

[James Tursa]

Maybe he wants the results presented in columns?

tmax = 50;
step = 5;
t = (0:step:tmax)'; % make it a column
X = [t,10*(1 - exp(-0.2*t))]; % put the result in columns

[Athanasios Naminsenoiazi]

Did that later on the code. Didn't post it all because 1.) It works and 2.) he specifically said that the formula is wrong...

[James Tursa]

Wrong in what way? The code does match the formula you posted. Is there another formula you should be using?