r the element  function <IMG
 WIDTH="13" HEIGHT="17" ALIGN="MIDDLE" BORDER="0"
 SRC="img36.png"
 ALT="$f_j$"> are  the variables  <IMG
 WIDTH="8" HEIGHT="8" ALIGN="BOTTOM" BORDER="0"
 SRC="img37.png"
 ALT="$v$"> and, while we
need to associate  the particular values  <IMG
 WIDTH="14" HEIGHT="16" ALIGN="MIDDLE" BORDER="0"
 SRC="img38.png"
 ALT="$\bar{x}_j$"> with <IMG
 WIDTH="8" HEIGHT="8" ALIGN="BOTTOM" BORDER="0"
 SRC="img39.png"
 ALT="$v$">,  it is
the elemental variables which are important in defining  