dual-class {salad}

dual class

Description

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

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.

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.

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)