dear members,
I have the following nls output:
Formula: YLf13 ~ (d + e * ((XL)^(1/3)) + f * log(LM3 + 18.81))
Parameters:
Estimate Std. Error t value Pr(>|t|)
d 5.892e-09 8.644e-10 6.817 2.06e-11 ***
e -6.585e-09 5.518e-10 -11.934 < 2e-16 ***
f 1.850e-10 2.295e-10 0.806 0.42
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Signif. codes: 0 ?***? 0.001 ?**? 0.01 ?*? 0.05 ?.? 0.1 ? ? 1
Residual standard error: 9.57e-10 on 677 degrees of freedom
Number of iterations to convergence: 2
Achieved convergence tolerance: 3.973e-08
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Residual sum of squares: 6.2e-16
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t-based confidence interval:
2.5% 97.5%
d 4.195378e-09 7.589714e-09
e -7.668142e-09 -5.501342e-09
f -2.655647e-10 6.354852e-10
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Correlation matrix:
d e f
d 1.0000000 -6.202339e-01 -7.832539e-01
e -0.6202339 1.000000e+00 -2.127301e-05
f -0.7832539 -2.127301e-05 1.000000e+00
if I let XL = 1.1070513 and LM3 = 0.3919 , and consider the coeffs as given above, the right hand side of the above equation is negative.
But YLf13 is always positive! How is this possible? Am I interpreting the result of the nls output properly? Should I interpret the coeffs differently? I have done hours of thinking over the above problem but couldn't find any results...
I cannot provide the full values of YLf13, XL and LM3 due to IPR issues....please cooperate......however, if the only way to solve the problem is to give these values, I would indeed give them.....
Also forgive me if there is a minor mistake in my calculations... or a typo....
very many thanks for your time and effort....
yours sincerely,
AKSHAY M KULKARNI