cNORM (version 2.0.1)

prepareData: Prepare data for modeling in one step (convenience method)

Description

This is a convenience method to either load the inbuilt sample dataset, or to provide a data frame with the variables "raw" (for the raw scores) and "group" The function ranks the data within groups, computes norm values, powers of the norm scores and interactions. Afterwards, you can use these preprocessed data to determine the best fitting model.

Usage

prepareData(
  data = NULL,
  group = "group",
  raw = "raw",
  age = "group",
  k = 4,
  width = NA,
  weights = NULL,
  scale = "T",
  descend = FALSE,
  silent = FALSE
)

Arguments

data

data.frame with a grouping variable named 'group' and a raw score variable named 'raw'.

group

grouping variable in the data, e. g. age groups, grades ... Setting group = FALSE deactivates modeling in dependence of age. Use this in case you do want conventional norm tables.

raw

the raw scores

age

the continuous explanatory variable; by default set to "group"

k

The power parameter, default = 4

width

if a width is provided, the function switches to rankBySlidingWindow to determine the observed raw scores, otherwise, ranking is done by group (default)

weights

Vector or variable name in the dataset with weights for each individual case. It can be used to compensate for moderate imbalances due to insufficient norm data stratification. Weights should be numerical and positive. Please note, that this feature is currently EXPERIMENTAL and subject to ongoing work! Precision of weighting increases with sample size. On the other hand, in large samples, it is easy to stratificate and then weighting is not needed anymore.

scale

type of norm scale, either T (default), IQ, z or percentile (= no transformation); a double vector with the mean and standard deviation can as well, be provided f. e. c(10, 3) for Wechsler scale index point

descend

ranking order (default descent = FALSE): inverses the ranking order with higher raw scores getting lower norm scores; relevant for example when norming error scores, where lower scores mean higher performance

silent

set to TRUE to suppress messages

Value

data frame including the norm scores, powers and interactions of the norm score and grouping variable

See Also

Other prepare: computePowers(), rankByGroup(), rankBySlidingWindow()

Examples

# NOT RUN {
# conducts ranking and computation of powers and interactions with the 'elfe' dataset
data.elfe <- prepareData(elfe)

# use vectors instead of data frame
data.elfe <- prepareData(raw=elfe$raw, group=elfe$group)

# variable names can be specified as well, here with the BMI data included in the package
data.bmi <- prepareData(CDC, group = "group", raw = "bmi", age = "age")

# modeling with only one group with the 'elfe' dataset as an example
# this results in conventional norming
data.elfe2 <- prepareData(data = elfe, group = FALSE)
m <- bestModel(data.elfe2)
# }