earth (version 2.5-1)

evimp: Estimate variable importances in an "earth" object

Description

Estimate variable importances in an earth object

Usage

evimp(obj, trim=TRUE, sqrt.=FALSE)

Arguments

obj

An earth object.

trim

If TRUE (default), delete rows in the returned matrix for variables that don't appear in any subsets.

sqrt.

Default is FALSE. If TRUE, take the sqrt of the GCV and RSS importances before normalizing to 0 to 100. This arguably gives a better indication of relative importances because the raw importanc

Value

• See the example later. This function returns a matrix showing the relative importances of the variables in the model. There is a row for each variable. The row name is the variable name, but with -unused appended if the variable does not appear in the final model.

  The columns of the matrix are: col: column index of the variable in the x argument to earth. used: 1 if the variable is used in the final model, else 0. Equivalently, 0 if the row name has a -unused suffix. nsubsets: variable importance using the "number of subsets" criterion. Is the number of subsets that include the variable (see "Three Criteria" below). gcv: variable importance using the GCV criterion (see below). rss: variable importance using the RSS criterion (see below). The rows are sorted on the nsubsets criterion. This means that values in the nsubsets column decrease as you go down the column (more accurately, they are non-increasing). The values in the gcv and rss columns are also non-increasing, except where the gcv or rss ranking differs from the nsubsets ranking. For convenience scanning the columns by eye, there are unnamed columns (not listed above) after the gcv column and the rss column. These have a 0 where the ranking using the gcv or rss criteria differs from that using the nsubsets criterion. In other words, there is a 0 for values that increase as you go down the gcv or rss column.

See Also

earth, plot.evimp

Examples

data(ozone1)
a <- earth(O3 ~ ., data=ozone1, degree=2)
ev <- evimp(a, trim=FALSE, sqrt.=TRUE)
plot(ev)
print(ev)