a3 {A3}

A3 Results for Arbitrary Model

Description

This function calculates the A3 results for an arbitrary model construction algorithm (e.g. Linear Regressions, Support Vector Machines or Random Forests). For linear regression models, you may use the a3.lm convenience function.

Usage

a3(formula, data, model.fn, model.args = list(), ...)

Arguments

formula

the regression formula.

data

a data frame containing the data to be used in the model fit.

model.fn

the function to be used to build the model.

model.args

a list of arguments passed to model.fn.

...

additional arguments passed to a3.base.

Value

S3 A3 object; see a3.base for details

References

Scott Fortmann-Roe (2015). Consistent and Clear Reporting of Results from Diverse Modeling Techniques: The A3 Method. Journal of Statistical Software, 66(7), 1-23. <http://www.jstatsoft.org/v66/i07/>

Examples

 ## Standard linear regression results:

 summary(lm(rating ~ ., attitude))

 ## A3 Results for a Linear Regression model:

 # In practice, p.acc should be <= 0.01 in order
 # to obtain finer grained p values.

 a3(rating ~ ., attitude, lm, p.acc = 0.1)


 ## A3 Results for a Random Forest model:

 # It is important to include the "+0" in the formula
 # to eliminate the constant term.

 require(randomForest)
 a3(rating ~ .+0, attitude, randomForest, p.acc = 0.1)

 # Set the ntrees argument of the randomForest function to 100

 a3(rating ~ .+0, attitude, randomForest, p.acc = 0.1, model.args = list(ntree = 100))

 # Speed up the calculation by doing 5-fold cross-validation.
 # This is faster and more conservative (i.e. it should over-estimate error)

 a3(rating ~ .+0, attitude, randomForest, n.folds = 5, p.acc = 0.1)

 # Use Leave One Out Cross Validation. The least biased approach,
 # but, for large data sets, potentially very slow.

 a3(rating ~ .+0, attitude, randomForest, n.folds = 0, p.acc = 0.1)

 ## Use a Support Vector Machine algorithm.

 # Just calculate the slopes and R^2 values, do not calculate p values.

 require(e1071)
 a3(rating ~ .+0, attitude, svm, p.acc = NULL)