X-ray pixel intensities over time

The Pixel data frame has 102 rows and 4 columns of data on the pixel intensities of CT scans of dogs over time

Format

This data frame contains the following columns:

Dog

a factor with levels 1 to 10 designating the dog on which the scan was made

Side

a factor with levels L and R designating the side of the dog being scanned

day

a numeric vector giving the day post injection of the contrast on which the scan was made

pixel

a numeric vector of pixel intensities

Source

Pinheiro, J. C. and Bates, D. M. (2000) Mixed-effects Models in S and S-PLUS, Springer.

Examples

fm1 <- lme(pixel ~ day + I(day^2), data = Pixel,
           random = list(Dog = ~ day, Side = ~ 1))
#> Error in solve.default(do.call("cbind", Xcols), apply(shifted, 2, fun,     ...)): Lapack routine dgesv: system is exactly singular: U[21,21] = 0
summary(fm1)
#> Error: object 'fm1' not found
VarCorr(fm1)
#> Error: object 'fm1' not found