pairs.lmList              package:nlme              R Documentation

Pairs Plot of an lmList Object

Description:

     Diagnostic plots for the linear model fits corresponding to the
     'x'  components  are obtained. The 'form' argument gives
     considerable  flexibility in the type of plot specification. A
     conditioning  expression (on the right side of a '|' operator)
     always implies  that different panels are used for  each level of
     the conditioning  factor, according to a Trellis display. The
     expression on the right  hand side of the formula, before a '|'
     operator, must evaluate to  a data frame with at least two
     columns. If the data frame has two  columns, a scatter plot of the
     two variables is displayed (the Trellis  function 'xyplot' is
     used). Otherwise, if more than two columns  are present, a scatter
     plot matrix with pairwise scatter plots of the  columns in the
     data frame is displayed (the Trellis function  'splom' is used).

Usage:

     ## S3 method for class 'lmList':
     pairs(x, form, label, id, idLabels, grid, ...)

Arguments:

       x: an object inheriting from class 'lmList', representing a list
          of 'lm' objects with a common model. 

    form: an optional one-sided formula specifying the desired type of
          plot. Any variable present in the original data frame used to
          obtain 'x' can be referenced. In addition, 'x' itself can be
          referenced in the formula using the symbol '"."'. Conditional
          expressions on the right of a '|' operator can be used to
          define separate panels in a Trellis display. The expression
          on the right hand side of 'form', and to the left of the '|'
          operator, must evaluate to a data frame with at least two
          columns. Default is '~ coef(.) ', corresponding to a pairs
          plot of the coefficients of 'x'. 

   label: an optional character vector of labels for the variables in
          the pairs plot.

      id: an optional numeric value, or one-sided formula. If given as
          a value, it is used as a significance level for an outlier
          test based on the Mahalanobis distances of the estimated
          random effects. Groups with random effects distances greater
          than the 1-value percentile of the appropriate chi-square
          distribution are identified in the plot using 'idLabels'. If
          given as a one-sided formula, its right hand side must
          evaluate to a  logical, integer, or character vector which is
          used to identify points in the plot. If missing, no points
          are identified. 

idLabels: an optional vector, or one-sided formula. If given as a
          vector, it is converted to character and used to label the
          points identified according to 'id'. If given as a one-sided
          formula, its right hand side must evaluate to a vector which
          is converted to character and used to label the identified
          points. Default is the innermost grouping factor.  

    grid: an optional logical value indicating whether a grid should be
          added to plot. Default is 'FALSE'.

     ...: optional arguments passed to the Trellis plot function. 

Value:

     a diagnostic Trellis plot.

Author(s):

     Jose Pinheiro Jose.Pinheiro@pharma.novartis.com and Douglas Bates
     bates@stat.wisc.edu

See Also:

     'lmList', 'pairs.lme',  'pairs.compareFits',  'xyplot', 'splom'

Examples:

     fm1 <- lmList(distance ~ age | Subject, Orthodont)
     # scatter plot of coefficients by gender, identifying unusual subjects
     pairs(fm1, ~coef(.) | Sex, id = 0.1, adj = -0.5)    
     # scatter plot of estimated random effects
     ## Not run: 
     pairs(fm1, ~ranef(.))
     ## End(Not run)

