Biexponential model

DESCRIPTION:

This selfStart model evaluates the biexponential model function and its gradient. It has an initial attribute that creates initial estimates of the parameters A1, lrc1, A2 , and lrc2.

USAGE:

SSbiexp(input, A1, lrc1, A2, lrc2) 

REQUIRED ARGUMENTS:

input
a numeric vector of values at which to evaluate the model.
A1
a numeric parameter representing the multiplier of the first exponential.
lrc1
a numeric parameter representing the natural logarithm of the rate constant of the first exponential.
A2
a numeric parameter representing the multiplier of the second exponential.
lrc2
a numeric parameter representing the natural logarithm of the rate constant of the second exponential.

VALUE:

a numeric vector of the same length as input. It is the value of the expression A1*exp(-exp(lrc1)*input)+A2*exp(-exp(lrc2)*input). If all of the arguments A1, lrc1, A2, and lrc2 are names of objects, the gradient matrix with respect to these names is attached as an attribute named gradient.

SEE ALSO:

,

EXAMPLES:

Indo.1 <- Indometh[Indometh$Subject == 1, ] 
SSbiexp( Indo.1$time, 3, 1, 0.6, -1.3 )  # response only 
A1 <- 3 
lrc1 <- 1 
A2 <- 0.6 
lrc2 <- -1.3 
SSbiexp( Indo.1$time, A1, lrc1, A2, lrc2 ) # response and gradient