| makeItems {LikertMakeR} | R Documentation |
Synthetic rating-scale data with given first and second moments and a predefined correlation matrix
Description
makeItems() generates a dataframe of random discrete
values so the data replicate a rating scale,
and are correlated close to a predefined correlation matrix.
makeItems() is wrapper function for:
-
lfast(), generates a dataframe that best fits the desired moments, and -
lcor(), which rearranges values in each column of the dataframe so they closely match the desired correlation matrix.
Usage
makeItems(n, means, sds, lowerbound, upperbound, cormatrix)
Arguments
n |
(positive, int) sample-size - number of observations |
means |
(real) target means: a vector of length k of mean values for each scale item |
sds |
(positive, real) target standard deviations: a vector of length k of standard deviation values for each scale item |
lowerbound |
(positive, int) a vector of length k (same as rows & columns of correlation matrix) of values for lower bound of each scale item (e.g. '1' for a 1-5 rating scale) |
upperbound |
(positive, int) a vector of length k (same as rows & columns of correlation matrix) of values for upper bound of each scale item (e.g. '5' for a 1-5 rating scale) |
cormatrix |
(real, matrix) the target correlation matrix: a square symmetric positive-semi-definite matrix of values ranging between -1 and +1, and '1' in the diagonal. |
Value
a dataframe of rating-scale values
Examples
## define parameters
n <- 16
dfMeans <- c(2.5, 3.0, 3.0, 3.5)
dfSds <- c(1.0, 1.0, 1.5, 0.75)
lowerbound <- rep(1, 4)
upperbound <- rep(5, 4)
corMat <- matrix(
c(
1.00, 0.30, 0.40, 0.60,
0.30, 1.00, 0.50, 0.70,
0.40, 0.50, 1.00, 0.80,
0.60, 0.70, 0.80, 1.00
),
nrow = 4, ncol = 4
)
## apply function
df <- makeItems(
n = n, means = dfMeans, sds = dfSds,
lowerbound = lowerbound, upperbound = upperbound, cormatrix = corMat
)
## test function
str(df)
# means
apply(df, 2, mean) |> round(3)
# standard deviations
apply(df, 2, sd) |> round(3)
# correlations
cor(df) |> round(3)