how do I plot a logistic curve

  • Thread starter Thread starter TRUSSMAN
  • Start date Start date
T

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.
 
I'm a little bit confused. What is the value of b? Are the pairs (t,Y)? Is
t in seconds or minutes?
 
t is in years, the value of b (slope) differs depending on the value of t,
and yes the pairs are (t,Y)
 
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("A1:D4") for Params
 
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