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mgcv
Builds the design matrix and the penalty matrix for cubic regression splines.
crs(x, knots = NULL, df = 10, intercept = TRUE)
List of three elements
design matrix
penalty matrix
vector of knots (specified or calculated from df)
df
Numeric vector
Numeric vectors that specifies the knots of the splines (including boundaries); default is NULL
numeric value that indicates the number of knots desired (or degrees of freedom) if knots=NULL; default is 10
if FALSE, the intercept is excluded from the basis; default is TRUE
See package mgcv and section 4.1.2 of Wood (2006) for more details about this basis
Wood, S. N. (2006), Generalized additive models: an introduction with R. London: Chapman & Hall/CRC.
x <- seq(1,10,length=100) # natural cubic spline with 3 knots crs(x,knots=c(1,5,10))
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