rcspline.restate(knots, coef, type=c("ordinary","integral"), x="X", lx=nchar(x), norm=2, columns=65, before="& &", after="\", begin="", nbegin=0, digits=max(8, .Options$digits))
coef
is
k-1
, where
k=length(knots)
, the first coefficient must be
for the linear term and remaining
k-2
coefficients
must be for the constructed terms (e.g., from
rcspline.eval
).
If the length of
coef
is
k
, an intercept is assumed to be in
the first element.
type="integral"
to instead represent
its anti-derivative.
x
to count with respect to
columns
. Default is length
of character string contained by
x
. You may want to set
lx
smaller than this if it includes non-printable LaTeX commands.
rcspline.eval
for definitions.
"& &"
for an equation
array environment in LaTeX where you want to have a left-hand prefix
e.g.
f(X) & = &
or using
\lefteqn
.
begin
knots
is a vector of knots,
latex
is a vector of text strings
with the LaTeX representation of the formula.
columns.used
is the number of columns used in the output string
since the last newline command.
function
is an S function, which is
also return in character string format as the
text
attribute.
Frank Harrell
Department of Biostatistics, Vanderbilt University
f.harrell@vanderbilt.edu
set.seed(1) x <- 1:100 y <- x + rnorm(100, 0, 5) xx <- rcspline.eval(x, inclx=TRUE, nk=4) knots <- attr(xx, "knots") coef <- lsfit(xx, y)$coef options(digits=4) # rcspline.restate must ignore intercept w <- rcspline.restate(knots, coef[-1], x="{\\rm BP}") # could also have used coef instead of coef[-1], to include intercept cat(attr(w,"latex"), sep="\n") xtrans <- eval(attr(w, "function")) # This is an S function of a single argument plot(x, xtrans(x), type="l") # Plots fitted transformation #x <- blood.pressure xx.simple <- cbind(x, pmax(x-knots[1],0)^3, pmax(x-knots[2],0)^3, pmax(x-knots[3],0)^3, pmax(x-knots[4],0)^3) pred.value <- coef[1] + xx.simple %*% w plot(x, pred.value, type='l') # same as above