While function not stopping at correct point/ how do I get longer vectors for my variables

I am trying to plot for y <= 9.8

x(1) = 0;
y(1) = 0;
i = 1;
while y <= 9.8
    x(i+1) = x(i) + 0.001;
    y(i+1) = y(i) + 10*(exp(-x/4));
    
    i = i +0.1;
 
end
plot(x,y)

this results in the following graph

and x as a vector [0,1], and y as[0,10]

first, with the formula that I gave for y, y(i) + 10*(exp(-x/4)) when x = 1, should be 7.7880, so the maximum value of x should be greater than 1

second, why did the y value exceed 9.8?

third, how can I fix this so that i 1) I get more values in the vectors and 2) end where y = 9.8?

This is a homework problem, otherwise I would just create a longer vector for x, the answer must be using a while loop

much thanks

[Walter Roberson]

while y <= 9.8
    

means the same thing as

while all(y <= 9.8)

This is important because your y is a vector.

Your code does not generate the output you show: your code generates an error message about left and right side having different number of elements. In your computation of y(i+1) you use x which is the entire vector x, so the size of the right hand side is going to be the same as the current size of x.