void xlog (xori, xmax, yformat, yori, yste, ymax) LOGPLT.C Level 2
float xori  The value of x at the left-hand end of the x axis.
float xmax  The value of x at the right-hand end of the x axis.
char *yformat  The format which will be used for the y axis labels. Use %e, %f, or %g 
formats ("%-1.0f" for integer labels), enclosed in double quotes.
float yori  The value of y at the bottom of the y axis.
 float ystep The change in y between each two tick marks on the y axis.
float ymax  he value of y at the top of the y axis.
xlog() is used to plot data with a logarithmic x axis and linear y axis. It may be called before the datum points are generated if the scales are known in advance. For a self-scaling version of this function, see xlgscle(). xori and xmax need not be even decades but they should have only one significant figure (e.g., 2., .03, 500., ...).