ffAnova | R Documentation |

Analysis of variance table for a linear model using type `II`

* sums of squares,
which are described in Langsrud et al. (2007).
Type `II`

* extends the type `II`

philosophy to continuous variables.
The results are invariant to scale changes and pitfalls are avoided.

ffAnova(formula, data = NULL)

`formula` |
A model |

`data` |
An optional data frame, list or environment. |

This function is a variant of `ffmanova`

for the univariate special case.
The two input parameters will be interpreted by `model.frame`

.

An object of class `"anova"`

(see `anova`

).

Øyvind Langsrud and Bjørn-Helge Mevik

Langsrud, Ø., Jørgensen, K., Ofstad, R. and Næs, T. (2007):
“Analyzing Designed Experiments with Multiple Responses”,
*Journal of Applied Statistics*, **34**, 1275-1296.

# Generate example data set.seed(123) a <- c(0, 0, 0, 10, 10, 10, 1, 1, 1) A <- as.character(a) # A is categorical b <- 1:9 y <- rnorm(9)/10 + a # y depends strongly on a (and A) a100 <- a + 100 # change of scale (origin) b100 <- b + 100 # change of scale (origin) # Four ways of obtaining the same results ffAnova(y ~ A * b) ffAnova(y ~ A * b100) ffAnova(lm(y ~ A * b)) ffAnova(y ~ A * b, data.frame(A = A, y = y, b = 1:9)) # Second order continuous variable ffAnova(y ~ a + I(a^2)) # Model equivalent to 'y ~ A * b' ffAnova(y ~ (a + I(a^2)) * b) # Demonstrating similarities and differences using package car if (!require(car)) # Package car is loaded if available Anova <- function(...) { # Replacement function if car not available warning("No results since package car is not available")} lm_Ab <- lm(y ~ A * b) lm_Ab100 <- lm(y ~ A * b100) # Type II same as type II* in this case Anova(lm_Ab) # Type II Anova(lm_Ab100) # Type II ffAnova(lm_Ab) # Type II* ffAnova(lm_Ab100) # Type II* # Type III depends on scale Anova(lm_Ab, type = 3) Anova(lm_Ab100, type = 3) lm_a <- lm(y ~ a + I(a^2)) lm_a100 <- lm(y ~ a100 + I(a100^2)) # Now Type II depends on scale Anova(lm_a) # Type II Anova(lm_a100) # Type II ffAnova(lm_a) # Type II* ffAnova(lm_a100) # Type II*

Embedding an R snippet on your website

Add the following code to your website.

For more information on customizing the embed code, read Embedding Snippets.