The two functions
ga_anova are for fitting generalised additive models (
gam) with the
mgcv package. It will use the
gam() function in
mgcv for ANOVA designs with up to two categorical fixed factors (with two or more levels;
Fixed_Factor), and exactly one factor is a continuous variable (e.g. time), which is called
Smooth_Factor. A smooth function is fitted with factor-wise smooth basis function (
by = ). A default value for number of nodes (the argument
gam) may work, but a specific number can be provided using the
Nodes argument. The model is fit using the
REML method. When two categorical fixed factors are provided, an interaction term is included for main effects and smooth basis functions.
ga_anova( data, Y_value, Fixed_Factor, Smooth_Factor, Random_Factor = NULL, Nodes = NULL, ... )
a data frame where categorical independent variables are converted to factors using
as.factor() first. The function will throw errors without this.
name of column containing quantitative (dependent) variable, provided within "quotes".
name(s) of categorical fixed factors (independent variables) provided as a vector if more than one or within "quotes". Convert to factors first with
the continuous variable to fit smoothly with a basis function, provided within "quotes" (only 1 Smooth_Factor allowed).
name(s) of random factors to be provided in "quotes" (only 1 Random_Factor allowed). Convert to factor with
number of nodes (the parameter
any additional variables to pass on to
ANOVA table of class "anova" and "data.frame".
Random_Factor is also provided, it is fitted using
bs = "re" smooth.
#with zooplankton data ga_anova(data = data_zooplankton, Y_value = "log(density_adj)", Fixed_Factor = "taxon", Smooth_Factor = "day") #> #> Family: gaussian #> Link function: identity #> #> Formula: #> log(density_adj) ~ taxon + s(day, by = taxon) #> #> Parametric Terms: #> df F p-value #> taxon 3 23.97 4.97e-15 #> #> Approximate significance of smooth terms: #> edf Ref.df F p-value #> s(day):taxonCalanoid copepods 7.828 8.643 28.267 < 2e-16 #> s(day):taxonD. thomasi 6.989 8.057 42.695 < 2e-16 #> s(day):taxonK. cochlearis 5.349 6.470 5.739 5.76e-06 #> s(day):taxonL. siciloides 3.076 3.825 5.322 0.000466