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% File src/library/splines/man/ns.Rd
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% File src/library/splines/man/ns.Rd
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% Part of the R package, https://www.R-project.org
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% Part of the R package, https://www.R-project.org
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% Copyright 1995-2017 R Core Team
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% Copyright 1995-2018 R Core Team
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% Distributed under GPL 2 or later
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% Distributed under GPL 2 or later
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\name{ns}
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\name{ns}
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\alias{ns}
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\alias{ns}
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\title{Generate a Basis Matrix for Natural Cubic Splines}
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\title{Generate a Basis Matrix for Natural Cubic Splines}
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## To see what knots were selected
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## To see what knots were selected
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attr(terms(fm1), "predvars")
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attr(terms(fm1), "predvars")
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## example of safe prediction
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## example of safe prediction
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plot(women, xlab = "Height (in)", ylab = "Weight (lb)")
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plot(women, xlab = "Height (in)", ylab = "Weight (lb)")
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ht <- seq(57, 73, length.out = 200)
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ht <- seq(57, 73, length.out = 200) ; nD <- data.frame(height = ht)
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lines(ht, predict(fm1, data.frame(height = ht)))
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lines(ht, p1 <- predict(fm1, nD))
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stopifnot(all.equal(p1, predict(update(fm1, . ~
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                            splines::ns(height, df=5)), nD)))
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          # not true in R < 3.5.0
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\dontshow{
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\dontshow{
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## Consistency:
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## Consistency:
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x <- c(1:3, 5:6)
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x <- c(1:3, 5:6)
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stopifnot(identical(ns(x), ns(x, df = 1)),
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stopifnot(identical(ns(x), ns(x, df = 1)),
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          identical(ns(x, df = 2),
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          identical(ns(x, df = 2), ns(x, df = 2, knots = NULL)), # not true till 2.15.2
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                    ns(x, df = 2, knots = NULL)), # not true till 2.15.2
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          !is.null(kk <- attr(ns(x), "knots")), # not true till 1.5.1
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          !is.null(kk <- attr(ns(x), "knots")), # not true till 1.5.1
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          length(kk) == 0)
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          length(kk) == 0)
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}
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}
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}
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}
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\keyword{smooth}
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\keyword{smooth}