Displaying 3 results from an estimated 3 matches for "photosynthetic".
Did you mean:
photosynthesis
2004 Apr 01
1
nls function
Hello. I am trying to fit a non-rectangular hyperbola function to data
of photosynthetic rate vs. light intensity. There are 4 parameters that
have to be estimated. I find the nls function very difficult to use
because it often fails to converge and then gives out cryptic error
messages. I have tried playing with the control parameters but this
does not always help.
Is there anothe...
2005 Oct 26
0
self starting function for nonlinear least squares.
...of this morning, concerning a problem that I am
having constructing a self-starting function for use with nls (and
eventually with nlsList and nlme), the following is the self-starting
function called NRhyperbola:
> NRhyperbola
function (Irr,theta,Am,alpha,Rd)
{
# Am is the maximum gross photosynthetic rate
# Rd is the dark resiration rate (positive value)
# theta is the shape parameter
# alpha is the initial quantum yeild
#
(1/(2*theta))*
(alpha*Irr + Am - sqrt((alpha*Irr + Am)^2 -4*alpha*theta*Am*Irr))- Rd
}
attr(,"initial")
function (mCall, LHS, data)
{
xy <- sorte...
2005 Oct 26
1
help with a self-starting function in nonlinear least squares regression.
Hello. I am having a problem setting up a self-starting function for
use in nonlinear regression (and eventually in the mixed model version).
The function is a non-rectangular hyperbola - called "NRhyperbola" -
which is used for fitting leaf photosynthetic rate to light intensity.
It has one independent variable (Irr) and four parameters (theta, Am,
alpha and Rd). I have created this to act as a self-starting function.
The self-starting function seems to work (i.e. when I call "getInitial"
it provides the initial values), but I can't g...