R: Extract Matrix or St Fitsent in the original data frame used to obtain <code>y</code> can be referenced. In addition, <code>y</code> itself can be referenced in the formula using the symbol <code>"."</code>. Conditional expressions on the right of a <code>|</code> operator can be used to define separate panels in a Trellis display. The expression on the right hand side of <code>form</code> and to the left of a <code>|</code> operator must evaluate to a residuals vector, or a random effects matrix. Default is <code>~ resid(., type = "p")</code>, corresponding to a normal plot of the standardized residuals evaluated at the innermost level of nesting.</td></tr> <tr valign="top"><td><code>abline</code></td> <td> an optional numeric value, or numeric vector of length two. If given as a single value, a horizontal line will be added to the plot at that coordinate; else, if given as a vector, its values are used as the intercept and slope for a line added to the plot. If missing, no lines are added to the plot.</td></tr> <tr valign="top"><td><code>id</code></td> <td> an optional numeric value, or one-sided formula. If given as a value, it is used as a significance level for a two-sided outlier test for the standardized residuals (random effects). Observations with absolute standardized residuals (random effects) greater than the <i>1 - value/2</i> quantile of the standard normal distribution are identified in the plot using <code>idLabels</code>. 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 observations in the plot. If missing, no observations are identified.</td></tr> <tr valign="top"><td><code>idLabels</code></td> <td> an optional vector, or one-sided formula. If given as a vector, it is converted to character and used to label the observations identified according to <code>id</code>. 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 observations. Default is the innermost grouping factor.</td></tr> <tr valign="top"><td><code>grid</code></td> <td> an optional logical value indicating whether a grid should be added to plot. Default is <code>FALSE</code>.</td></tr> <tr valign="top"><td><code>...</code></td> <td> optional arguments passed to the Trellis plot function.</td></tr> </table> <h3>Value</h3> <p> a diagnostic Trell