Terry,
There are lots of different functions that meet your criteria. Below is
an easy one that might work.
f <- function(x, scale, power) ifelse(x <=0, 0, 1 -exp(-(x/scale)^power))
Scale and power are scalars and must be strictly greater than 0. Plot
some examples to see how it fits your data and your expectations.
Dave
From:
"Beutel, Terry S" <terry.beu...@deedi.qld.gov.au>
To:
"r-sig-ecology@r-project.org" <r-sig-ecology@r-project.org>
Date:
04/12/2012 11:17 PM
Subject:
[R-sig-eco] Which function would fit these data (Version 2)
Sent by:
r-sig-ecology-boun...@r-project.org
Hi list members
Sending this again as symbols in the previous version did not translate.
Apologies if this is not too specifically R related, but I am looking fit
a model to some simulated data. X is distance to sample point, y is binary
outcome (present/absent). I was hoping someone can suggest a (presumably)
non linear function that might meet the following criteria
A. 0 <= y <=1 (actual responses are binary)
B. xmax = infinity
C. xmin <= 0
D. Where x = 0 then y >= 0
E. Where x equals Infinity then y equals 1
F. As x approaches Infinity from xmin, the slope of the function
declines monotonically toward 0.
Thanks in advance for any suggestions
Dr Terry Beutel
Agri-Science Queensland
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