ds = dataset you are currently using.
DV = dependent variable of interest
IV = independent variable of interest
XYXY = dummy name for a variable, matrix, or data frame into which you are moving information.
Extract descriptives, by levels of independent variable as.factor!!!!!
Step 1: Tell R that your independent variables have discrete levels
R assumes that variables are continuous. In order to tell it otherwise, use the factor function.
ds$IV <- as.factor(ds$IV)
ds$Subject <- as.factor(ds$Subject)
At this step, you can also add labels to the data if you desire
ds$IV <- factor(ds$IV,
levels = c(0,1),
labels = c("Label for 0", "Label for 1"))
Step 2: Extract descriptives
The psych package includes a describeBy function that allows descriptives to be produced with respect to any independent variables.
To get main effects, simply only include one IV
mat=TRUE outputs data in a matrix format, which makes it easier to work with
again, type refers to the manner in which skew and kurtosis are calculated
Per Joanes and Gill (1998), type 2 has been adopted by SPSS, SAS, and Excel
digits=2 refers to the number of significant digits reported. Adjust as needed
group = ds$IV1 : ds$IV2,
type = 2,
digits = 2)