10.7  TYPES 

Data  may  either  be  X,Y,Z  points or mesh data.  A point consists of an
X,Y,[Z] value with optional errors DX,DY,[DZ],[NDX], [NDY],[NDZ] Z and  DZ
are  optional and may not necessarily be present.  MESH data is a data set
consisting of Z values as a function of X and Y.  A mesh is essentially  a
square  grid of data with X,Y vs Z.  A mesh may also have optional DX, DY,
and DZ values attached to it.

Data  may  be  subdivided  into  data  sets.   Each  data  set is numbered
consecutively starting with 1.   Within  each  data  set  the  points  are
numbered  from 1 to n.  To create a new data set use the DATA SET command.
Some commands such as FIT allow automatic creation of a new  data  set  if
the option APPEND is used.

When  plotting  you  may  specify which data set you wish to plot with the
option SET=n.  For example PLOT SET=1 plots the first data set.   You  may
also  use  FIRST,LAST,NEXT,PREVIOUS,  or  CURRENT  to  specify a data set.
FIRST is always set number 1 while  LAST  is  the  number  of  data  sets.
CURRENT is the last set specified.  NEXT is the current data set +1, while
PREVIOUS is the current set -1.
 
For example you may plot 2 sets by:
     TD:PLOT SET=FIRST
     TD:PLOT SET=NEXT
You may also specify a range of sets.
     TD:PLOT SET=2 TO LAST
plots all data sets except for number 1.
                                  Warning
When plotting multiple data sets, the format of the plot is taken from the
first data set.  If the first set is a mesh, the plot will be 3-D.