Plot only Q-Q from ANOVA

Hi, and welcome!

One way to do this is with `qqPlot()` in the cars package, although you do get an envelope to go with it.

From `help(aov)` first example

``````library(car)
op <- options(contrasts = c("contr.helmert", "contr.poly"))
( npk.aov <- aov(yield ~ block + N*P*K, npk) )
#> Call:
#>    aov(formula = yield ~ block + N * P * K, data = npk)
#>
#> Terms:
#>                    block        N        P        K      N:P      N:K
#> Sum of Squares  343.2950 189.2817   8.4017  95.2017  21.2817  33.1350
#> Deg. of Freedom        5        1        1        1        1        1
#>                      P:K Residuals
#> Sum of Squares    0.4817  185.2867
#> Deg. of Freedom        1        12
#>
#> Residual standard error: 3.929447
#> 1 out of 13 effects not estimable
#> Estimated effects are balanced
summary(npk.aov)
#>             Df Sum Sq Mean Sq F value  Pr(>F)
#> block        5  343.3   68.66   4.447 0.01594 *
#> N            1  189.3  189.28  12.259 0.00437 **
#> P            1    8.4    8.40   0.544 0.47490
#> K            1   95.2   95.20   6.166 0.02880 *
#> N:P          1   21.3   21.28   1.378 0.26317
#> N:K          1   33.1   33.14   2.146 0.16865
#> P:K          1    0.5    0.48   0.031 0.86275
#> Residuals   12  185.3   15.44
#> ---
#> Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
coefficients(npk.aov)
#> (Intercept)      block1      block2      block3      block4      block5
#>  54.8750000   1.7125000   1.6791667  -1.8229167  -1.0137500   0.2950000
#>          N1          P1          K1       N1:P1       N1:K1       P1:K1
#>   2.8083333  -0.5916667  -1.9916667  -0.9416667  -1.1750000   0.1416667
qqPlot(npk.aov)
``````

``````#> [1] 3 5
``````

Created on 2019-11-03 by the reprex package (v0.3.0)

BTW: Notice that I've used a reproducible example, called a reprex, which always helps questions get more answers.

2 Likes