@tomleslie  iam sory, i have done it in this sheet2_fit.mw
 

@tomleslie i am sory. how do I draw a graph with the values of K and r already found for t = 1...12.
2_fit.mw

@tomleslie i am sory there is a mistake for my program. i mistyped the exponential in my program. and I've fixed it. is this suitable?
can you help me to make the figure for t  t =10? thank yu very much
2_fit.mw

@tomleslie thank you for your program. maybe you cen help me if my equation is like this:
N(t) = K/(1+(((K/80)-1)*e^(-r*t))) . e is eksponensial. the program become error when use Exp. Thank for your help.
1_fit.mw1_fit.mw1_fit.mw1_fit.mw

@mmcdara . thank you for the program. i had saw the program and i confuse about rho and r. in this program you found rho = 0.0230521 , when rho=-r implies r = -0.0230521. based on the teory r should be positive because r is the population growth rate. 
let equation : 
N(t)= k/(1+((k/80)-1)e^(-r*t)))
in teory if t = 0 then N(t) = 80.
if t uproach to infinity then N(t) uproach to K or N(t) => K. but in this program obtained K = 10, far below the initial value N(t) = 80.
please advise
Thankyou Very much

@mmcdara thank you very much, you are very helpful.

@mmcdara is it the same if the kurve is

y=k/(1 + (k/80 - 1)*e^-(r*t)).

e is exp

@tomleslie 

thank you very much, i will learning it

@mmcdara 

thank you very much, i will learning it.

@Rouben Rostamian  thank you so much. i will edit my worksheet. Thank you very much for your help. 

Download faseportrait_3dAIS.mw

@Rouben Rostamian  i have upload my sheet. Thankyou very much