mars.to.earth {earth} | R Documentation |
Convert a ‘mars’ object to an ‘earth’ object
mars.to.earth(object)
object |
A ‘mars’ object, created using mars in the mda package.
|
The value is the same as that returned by earth
but
with skeletal versions of rssVec
, gcvVec
, and prune.terms
.
You can fully initialise these components by calling update.earth
after mars.to.earth
, but if you do this selected.terms
may change.
However with pmethod="backward"
a change is unlikely —
selected.terms
would change only if GCVs are so close that rounding
differences have an effect.
Perhaps the most notable difference between earth and mars objects
is that earth
returns bx
in $bx
, while
mars
returns bx
in $x
.
For details of other differences between mars
and
earth
objects,
see the comments in the function header in the source code of
mars.to.earth()
.
## Not run: # The example is not run with example("mars.to.earth") because that would # require making the earth package dependent on the mda package. library(mda) a <- mars(trees[,-3], trees[,3]) a <- mars.to.earth(a) summary(a, digits = 2) # the standard earth functions can now be used # yields (note the reconstructed call): # Call: # earth(x = trees[, -3], y = trees[, 3]) # # Expression: # 20 # + 5.4 * pmax(0, Girth - 12) # - 2.6 * pmax(0, 12 - Girth) # + 0.72 * pmax(0, Height - 76) # # Number of cases: 31 # Selected 4 of 5 terms, and 2 of 2 predictors # Number of terms at each degree of interaction: 1 3 (additive model) # GCV: 13 RSS: 251 GRSq: 0.95 RSq: 0.97 ## End(Not run)