# getbasismatrix: Values of Basis Functions or their Derivatives In fda: Functional Data Analysis

## Description

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

## Usage

 `1` ```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.

`eval.fd`
 ``` 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50``` ```## ## 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.) ## ## Use library(Matrix) ## bspl2.2 <- create.bspline.basis(norder=2, breaks=seq(0, 1, .5)) M2 <- getbasismatrix(seq(0, 1, .2), bspl2.2, returnMatrix=TRUE) M2. <- Matrix(c(1,.6,.2,0,0,0, 0,.4,.8,.8,.4,0, 0,0,0,.2,.6,1), 6) (M2-M2.) all(abs(M2-M2.)<1e-15) ## ## 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 <- seq(July4.1776, Apr30.1789, length.out=14) AmRevMatrix <- getbasismatrix(AmRevYears, BspRevolution) matplot(AmRevYears, AmRevMatrix, type='b') # Image is correct, but # matplot does not recogize the Date class of x # POSIXct AmRev.ct <- as.POSIXct1970(c('1776-07-04', '1789-04-30')) BspRev.ct <- create.bspline.basis(AmRev.ct) AmRevYrs.ct <- seq(AmRev.ct[1], AmRev.ct[2], length.out=14) AmRevMat.ct <- getbasismatrix(AmRevYrs.ct, BspRev.ct) matplot(AmRevYrs.ct, AmRevMat.ct, type='b') # Image is correct, but # matplot does not recogize the Date class of x ```