zscores: zscores from an lmsqreg system
In lmsqreg: LMS (Cole-Green Stat in Med 1992 quantile regression)

Description Usage Arguments Details Value Version information: References See Also Examples

View source: R/all.R

use quantile regression object to generate zscores for new data

1	zscores(y, x, obj)

`y`	y values for which z-scores are desired
`x`	x values corresponding to y values
`obj`	an object of class lmsqreg.fit

To construct M(x) and S(x), linear interpolation is used when x lies between x values on which obj was fit; constant extrapolation is used when x lies out of the range of x used to create obj. In the latter case, warning messages are produced with information on the magnitude of the discrepancy between x and the range of x on which obj was based.

A vector of z-scores (signed number of standard deviations between y and its median value given the corresponding x as determined by the lmsqreg.fit object. Specifically, the lmsqreg.fit object determines functions M(x) = med(Y|X=x) and S(x) = S.D.(Y|X=x), and the zscore for the observation (y,x) is (y-M(x))/S(x).

Document version 1.3 97/03/26 /usr16/stdevs/stdev0f/SLIBS/lmsqreg.dev.obs/SCCS/s.zscores.d

TJ Cole, PJ Green, Smoothing reference centile curves: The LMS method and penalized likelihood; Stat in Med, 1992 (p1305).

lmsqreg.fit

#> zscores(6,10,fff)
#[1] -0.03834572
#Warning messages:
#  constant extrap. from 10.0002 to 10 in: zscores(6, 10, fff)
## see lmsqreg.fit help for creation of fff; this example
## illustrates a minor extrapolation problem.