A subset of tree growth observations from a Ponderosa pine growth database.
The ppine data frame has 166 rows and 8 columns.
data(ppine)This data frame contains the following columns:
Altitude of the plot, in feet above mean sea level.
Summer moisture index is the ratio of growing season heating degree days to growing season precipitation.
Diameter of the tree at breast height (4.5 feet).
Total stem height for the tree.
Crown ratio code. The scale is from 1 to 9 where a crown class of one represents a crown ratio between 0 and 15 percent. A crown ratio code of 2 represents a crown ratio value between 16 and 25%,...,8=76-85%, 9 >=85%.
Plot basal area at the beginning of the growth period.
Five-year diameter increment.
Five-year height increment.
The exogenous variables are elev, smi, dbh,
tht, cr, and ba; the endogenous variables
dg and hg. There are no lagged variables in the dataset
and the observations are for a single remeasurement.
The data was provided by the USDA Forest Service Intermountain Research Station.