evimp {earth}  R Documentation 
Estimate variable importances in an earth object
Description
Estimate variable importances in an earth
object
Usage
evimp(object, trim=TRUE, sqrt.=TRUE)
Arguments
object 
An 
trim 
If 
sqrt. 
Default is 
Value
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 (not all of these are printed by print.evimp
):

col
: Column index of the variable in thex
argument toearth
. 
used
: 1 if the variable is used in the final model, else 0. Equivalently, 0 if the row name has anunused
suffix. 
nsubsets
: Variable importance using the "number of subsets" criterion. Is the number of subsets that include the variable (see "Three Criteria" in the chapter onevimp
in theearth
vignette “Notes on the earth package”). 
gcv
: Variable importance using the GCV criterion (see "Three Criteria"). 
gcv.match
: 1, except is 0 where the rank using thegcv
criterion differs from that using thensubsets
criterion. In other words, there is a 0 for values that increase as you go down thegcv
column. 
rss
: Variable importance using the RSS criterion (see "Three Criteria"). 
rss.match
: Likegcv.match
but for therss
.
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 nonincreasing).
The values in the gcv
and rss
columns
are also nonincreasing, except where the
gcv
or rss
rank differs from the nsubsets
ranking.
Note
There is a chapter on evimp
in the earth
package vignette
“Notes on the earth package”.
Acknowledgment
Thanks to Max Kuhn for the original evimp
code and for helpful discussions.
See Also
Examples
data(ozone1)
earth.mod < earth(O3 ~ ., data=ozone1, degree=2)
ev < evimp(earth.mod, trim=FALSE)
plot(ev)
print(ev)