text adds the strings given in the vector labels at the
coordinates given by x and y to the current iPlot. y may be missing since
xy.coords(x,y) is used for construction of the coordinates.itext(x, y=NULL, labels=seq(along=x), ax=NULL, ay=NULL, ..., plot = iplot.cur())xy.coords is
used to obtain the coordinates.x and y relative to the text. 0
means left resp. top and 1 means right/bottom. Therefore vertically
and horizontally centered text can be obtainediobj.optilines, iobj.opt