aniaania 发表于 2010-4-22 18:49 
请问怎么拟合这个回归公式阿? y=b+(a-b)/(1+cx)^d 谢谢各位高手指点阿
有四个参数 a b c d 。
用什么软件可以做阿?
I give u a simple solution in SAS.
Here it goes,
*** formula y=b+(a-b)/(1+cx)^d;
*simulate data;
data sim;
a=1; b=2; c=1; d=2;
do i = 1 to 30;
*independent variable;
x=2*ranuni(7789);
**error term;
err=rannor(7789);
y=b+(a-b)/(1+c*x)**d;
output;
end;
drop a b c d;
run;
proc print; run;
proc nlin data=sim;
parms a=0.5 b=1 c=0.3 d=5;
model y= b+(a-b)/(1+c*x)**d;
run;