how do I plot a logistic curve

[TRUSSMAN]

I need to fit a logistic curve to data points on a scatter plot to determine
if regression (r^2) values are closer to 1, then linear or exponential
regression lines. The formula is Y = N/1+Ab^-t where N = 281422, A =
281421, b = %increase/time (slope), and t = time (x axis) my data points are
as follows:
(0,38558),(10,49371),(20,62980),(30,76212),(40,92228),(50,106022),(60,123203),(70,132165),(80,151326),(90,179323),(100,203212),(110,226546),(120,248710),(130,281422) examples are greatly appreciated.

 

[Joel]

I'm a little bit confused. What is the value of b? Are the pairs (t,Y)? Is
t in seconds or minutes?

 

[TRUSSMAN]

t is in years, the value of b (slope) differs depending on the value of t,
and yes the pairs are (t,Y)

 

[Joel]

Use Linest, Logest, or Trend. These are worksheet function that you can put
on you worksheet or call the from VBA

worksheetfunctions.Linest(Parm1, Parm2, Parm3)
worksheetfunctions.Logest(Parm1, Parm2, Parm3)
worksheetfunctions.Trend(Parm1, Parm2, Parm3)

=Linest(Parm1, Parm2, Parm3)
=Logest(Parm1, Parm2, Parm3)
=Trend(Parm1, Parm2, Parm3)

See worksheet help for more details. In VBA use Range("A14") for Params