getbasismatrix {fda}

Values of Basis Functions or their Derivatives

Description

Evaluate a set of basis functions or their derivatives at a set of argument values.

Usage

getbasismatrix(evalarg, basisobj, nderiv=0, returnMatrix=FALSE)

Arguments

evalarg

a vector of arguments values.

basisobj

a basis object.

nderiv

a nonnegative integer specifying the derivative to be evaluated.

returnMatrix

logical: If TRUE, a two-dimensional is returned using a special class from the Matrix package.

Value

a matrix of basis function or derivative values. Rows correspond to argument values and columns to basis functions.

References

Ramsay, James O., Hooker, Giles, and Graves, Spencer (2009), Functional data analysis with R and Matlab, Springer, New York.

Ramsay, James O., and Silverman, Bernard W. (2005), Functional Data Analysis, 2nd ed., Springer, New York.

Ramsay, James O., and Silverman, Bernard W. (2002), Applied Functional Data Analysis, Springer, New York.

See Also

eval.fd

Examples

##
## Minimal example:  a B-spline of order 1, i.e., a step function
## with 0 interior knots:
##
bspl1.1 <- create.bspline.basis(norder=1, breaks=0:1)
m <- getbasismatrix(seq(0, 1, .2), bspl1.1)

# check
m. <- matrix(rep(1, 6), 6,
    dimnames=list(NULL, 'bspl') )

all.equal(m, m.)


##
## Date and POSIXct
##
# Date
July4.1776    <- as.Date('1776-07-04')
Apr30.1789    <- as.Date('1789-04-30')
AmRev         <- c(July4.1776, Apr30.1789)
BspRevolution <- create.bspline.basis(AmRev)
AmRevYears    <- as.numeric(seq(July4.1776, Apr30.1789, length.out=14))
AmRevMatrix   <- getbasismatrix(AmRevYears, BspRevolution)
matplot(AmRevYears, AmRevMatrix, type='b')

# POSIXct
AmRev.ct    <- as.POSIXct1970(c('1776-07-04', '1789-04-30'))
BspRev.ct   <- create.bspline.basis(AmRev.ct)
AmRevYrs.ct <- as.numeric(seq(AmRev.ct[1], AmRev.ct[2], length.out=14))
AmRevMat.ct <- getbasismatrix(AmRevYrs.ct, BspRev.ct)
matplot(AmRevYrs.ct, AmRevMat.ct, type='b')