Pixel                  package:nlme                  R Documentation

X-ray pixel intensities over time

Description:

     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:

     data(Pixel)
     fm1 <- lme(pixel ~ day + I(day^2), data = Pixel,
                random = list(Dog = ~ day, Side = ~ 1))
     summary(fm1)
     VarCorr(fm1)

