earth (version 4.1.0)

evimp: Estimate variable importances in an earth object

Description

Estimate variable importances in an earth object

Usage

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

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 TRUE, meaning take the sqrt of the GCV and RSS importances before normalizing to 0 to 100. Taking the square root gives a better indication of relative importances becau

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 thexargument toearth.
  • used: 1 if the variable is used in the final model, else 0. Equivalently, 0 if the row name has an-unusedsuffix.
  • nsubsets: Variable importance using the "number of subsets" criterion. Is the number of subsets that include the variable (see "Three Criteria" in the chapter onevimpin theearthvignette../doc/earth-notes.pdf{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 thegcvcriterion differs from that using thensubsetscriterion. In other words, there is a 0 for values that increase as you go down thegcvcolumn.
  • rss: Variable importance using the RSS criterion (see "Three Criteria").
  • rss.match: Likegcv.matchbut 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 non-increasing). The values in the gcv and rss columns are also non-increasing, except where the gcv or rss rank differs from the nsubsets ranking.

See Also

earth, plot.evimp

Examples

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