Triangle Plot for Soil Texture
------------------------------

AUTHOR:   Francesco Danuso, Ph.D.,
	  Universita degli Studi di Udine, Istituto di Produzione
	  Vegetale, Udine, Italy.
SUPPORT:  FAX, either
	  Dr. Danuso, (011)-39-432-558603, or
	  STB Editor, 602-860-1446
 
The program creates a texture triangle for clay/sand values for each observa-
tion in the data set. The file with the soil type network (triatex.dta) must 
be in the current directory unless an appropriate change is made to the code.
Moreover, the data file to be plotted must be in active memory prior to
invoking ^triatex^. The plotted variables are ^clay^ and ^sand^ with labels
of ^CLAY (%)^ and ^SAND (%)^. It should be cautioned that the file in memory will
be destroyed - but only from active memory.  Both ^triatex.ado^ and ^triatex.dta^,
in addition to the data set in memory (e.g., ^protex.dta^), are necessary for 
the program to function.

^triatex^ gives the user the initial options of saving the graphic and of
choosing a graph symbol-type.

Perform a ^label list^ on triatex.dta to observe soil types.



EXAMPLE:
--------

	. ^use protex^

	. ^describe^

	Contains data from c:\ado\protex.dta
	  Obs:    10 (max= 77051)
	 Vars:     2 (max=    99)
	  1.  clay        float  %9.0g
	  2.  sand        float  %9.0g
	 Sorted by:

	. ^triatex^

	               TRIANGLE FOR SOIL TEXTURE
	             (USDA classification scheme)

	 File name for the graphic (ENTER=do not save):
	 Symbol (O|S|T|o|d|p|.|i|[varname]): ^O^

         <<Screen clears and triangle graph is presented>>