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.