salad (version 1.2)

dual-class: dual class

Description

An S4 class for forward differentiation of vector and matrix computations.

Slots

x

the value of the object. Use the function `value` to access this slot.

d

a (named) list of derivatives. Use the function `d` to access this slot.

Details

A dual object can be either a vector or a matrix. It can contain derivatives with respect to several variables. The derivatives will have the same shape as the value.

The shape of an object can be changed using `dim<-`. Note that by default `as.matrix` and `as.vector` will send back a regular vector/matrix object, dropping the derivatives. See `salad` to change this behaviour if needed (this is not the recommended solution).

Many methods and functions have been redefined in the package, in order to allow to apply existing code to `dual` objects, with no or little change.

See Also

value, d, dual, salad.

Examples

# creating a vector of length 4
x <- dual( c(1,2,1,0) )
x
d(x)
# turning x into a matrix
dim(x) <- c(2,2)
x
d(x)
# and back into a vector
dim(x) <- NULL
x
# weighted sum of the elements of x
S <- sum(1:4 * x)
S
d(S)