scaleDiagnosis

scaleDiagnosis provides a number of diagnostics for a scale (an aggregative measure consisting of several items).

scaleDiagnosis(dat=NULL, items=NULL, plotSize=180, sizeMultiplier = 1,
               axisLabels = "none", scaleReliability.ci=FALSE, conf.level=.95,
               powerHist=TRUE, ...)

Arguments

dat

A dataframe containing the items in the scale. All variables in this dataframe will be used if items is NULL.
items

If not NULL, this should be a character vector with the names of the variables in the dataframe that represent items in the scale.
plotSize

Size of the final plot in millimeters.
sizeMultiplier

Allows more flexible control over the size of the plot elements
axisLabels

Passed to ggpairs function to set axisLabels.
scaleReliability.ci

TRUE or FALSE: whether to compute confidence intervals for Cronbach's Alpha and Omega (uses bootstrapping function in MBESS, takes a while).
conf.level

Confidence of confidence intervals for reliability estimates (if requested with scaleReliability.ci).
powerHist

Whether to use the default ggpairs histogram on the diagonal of the scattermatrix, or whether to use the powerHist version.
...

Additional arguments are passed on to powerHist.

Details

Function to generate an object with several useful statistics and a plot to assess how the elements (usually items) in a scale relate to each other, such as Cronbach's Alpha, omega, the Greatest Lower Bound, a factor analysis, and a correlation matrix.

Value

An object with the input and several output variables. Most notably:

scaleReliability

The results of scaleReliability.

pca

A Principal Components Analysis

fa

A Factor Analysis

describe

Decriptive statistics about the items

scatterMatrix

A scattermatrix with histograms on the diagonal and correlation coefficients in the upper right half.

Examples

### Note: the 'not run' is simply because running takes a lot of time,
###       but these examples are all safe to run!

# NOT RUN {
### This will prompt the user to select an SPSS file
scaleDiagnosis();

### Generate a datafile to use
exampleData <- data.frame(item1=rnorm(100));
exampleData$item2 <- exampleData$item1+rnorm(100);
exampleData$item3 <- exampleData$item1+rnorm(100);
exampleData$item4 <- exampleData$item2+rnorm(100);
exampleData$item5 <- exampleData$item2+rnorm(100);

### Use a selection of two variables
scaleDiagnosis(dat=exampleData, items=c('item2', 'item4'));

### Use all items
scaleDiagnosis(dat=exampleData);
# }