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Augment Model Data for Diagnostic Plots

Source: R/lm_plot.df.R
lm_plot.df.Rd

Generates an augmented data frame from a linear model object, including fitted values, residuals, leverage, Cook's distance, prediction intervals, and outlier/influence flags. This function prepares model diagnostics for plotting.

Usage

lm_plot.df(mdl, parms = lm_plot.parms(mdl))

Arguments

mdl

An object of class lm, representing the fitted linear model.

parms

List of plotting parameters, usually from lm_plot.parms().

Value

A data frame with augmented diagnostic variables, one row per observation.

Details

The returned data frame contains key statistics for each observation:

  • .id: Observation identifier

  • .sequence: Sequence index

  • .obs: Observed values

  • .fits: Fitted/predicted values

  • .resid: Residuals

  • .se.fit: Estimated standard error of fitted (mean) value

  • .lower.pi: Lower bound on 95% prediction interval of fitted value

  • .upper.pi: Upper bound on 95% prediction interval of fitted value

  • .std.resid: Standardized residuals

  • .stud.resid: Studentized residuals

  • .cooksd: Cook's distance

  • .hat: Leverage (diagonal of the hat matrix)

  • .quantile: Theoretical normal quantile of residuals

  • .is.outl: Flag for residual outlier ("outl" or "reg")

  • .is.infl: Flag for influential point ("infl" or "outl" or "reg")

  • .is.lev: Flag for high leverage point ("lev" or "infl" or "reg")

See also

influence, influence.measures, rstandard, rstudent, outlier

Examples

mdl <- lm(Sepal.Length ~ Sepal.Width, data = iris)
df <- lm_plot.df(mdl)
head(df)
#>   .id .sequence .obs    .fits     .resid    .se.fit .lower.pi .upper.pi
#> 1   1         1  5.1 5.744459 -0.6444588 0.09618352  4.102926  7.385992
#> 2   2         2  4.9 5.856139 -0.9561394 0.06795306  4.220127  7.492152
#> 3   3         3  4.7 5.811467 -1.1114672 0.07090891  4.174965  7.447969
#> 4   4         4  4.6 5.833803 -1.2338033 0.06769302  4.197833  7.469773
#> 5   5         5  5.0 5.722123 -0.7221227 0.10780077  4.077773  7.366472
#> 6   6         6  5.4 5.655114 -0.2551144 0.14702457  3.998939  7.311290
#>   .std.resid .stud.resid     .cooksd        .hat  .quantile .is.outl .is.infl
#> 1 -0.7864325  -0.7854139 0.004260169 0.013589132 -0.6744898      reg      reg
#> 2 -1.1627712  -1.1641660 0.004616605 0.006782791 -1.0954185      reg      reg
#> 3 -1.3520774  -1.3559020 0.006801185 0.007385705 -1.5273795      reg      reg
#> 4 -1.5004021  -1.5068286 0.007627752 0.006730978 -1.7907506      reg      reg
#> 5 -0.8827646  -0.8821026 0.006766613 0.017070023 -0.7609839      reg      reg
#> 6 -0.3142222  -0.3132634 0.001618927 0.031751938 -0.2104284      reg      reg
#>   .is.lev
#> 1     reg
#> 2     reg
#> 3     reg
#> 4     reg
#> 5     reg
#> 6     lev