Routines to handle references constructed with the
LMS method. Given a set of LMS values, the functions convert
z-scores to measurement centiles and vice versa.
Usage
zLMS(x, L = 1, M, S)
cLMS(z, L = 1, M, S)
Arguments
x
vector of measurements to be converted to z-scores.
z
scalar or vector of z-scores to be converted to measurements.
L
vector of Box-Cox transformation (lambda) values, L in the LMS method.
M
vector of medians (mu), M in the LMS method.
S
vector of coefficients of variation (sigma), S in the LMS method.
Value
zLMS and cLMS return a vector the same length as M.
Details
x, L, M and S should all be the same length. z
can be scalar or vector. The formulae converting x to z and vice versa are:
$$z = \frac{(x/M)^L - 1}{L S}$$
$$x = M (1 + L S z)^{1/L})$$
where L has 10^-7 added if it is zero. The LMS method is the same as the BCCG family in
the gamlss package.