void graf (xformat, xori, xste, xmax, yformat, yori, yste, ymax) LINPLT.C Level 2
 char *xformat The x axis format. Use a floating point conversion specification (see page 154 in Kernighan and Ritchie, The C Programming Language, Second Ed.). Since it is a character string, it must be enclosed in double quotes. For example: "%-3.2f". 
Use "%-1.0f" for integer labels. Because C automatically expands the format to accommodate the required number of characters, it is best to use a width (number to the left of the decimal point) that is too small. This ensures that the labels will be centered. %e and %g formats may also be used.
float xori  The value of x at the left-hand end of the x axis. (User units.)
float xstep  The change in x between each two tick marks on the x axis.
float xmax  The value of x at the right-hand end of the x axis.
char *yformat  The y axis format (see above).
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 The value of y at the top of the y axis.
graf() is the primary axis setup routine for x-y plots. Because you supply the maximum and minimum values of the variables, graf() may be called either before or after the data are calculated or entered. Any values of x and y that lie beyond the axes boundaries will be cropped.

A word of caution: graf() arranges the axis parameters so the step size you specified will give a whole number of steps from ?ori to ?max. The maximum value will be adjusted as needed. For example, if you called

graf("%1.2f", 0.0f, 3.0f, 11.0f, "%1.2f", 0.0f, 3.0f, 14.0f)
the x axis would go from 0 to 12 and the y axis would go from 0 to 15. Also, if you do not specify enough precision in the label formats the labels may look as if they do not make sense. For example, if your step size is 0.002 and your format string is "%1.2f " the value of the labels would change only every fifth step. If graf() does need to adjust the axis limits the plot scaling will be corrected to reflect the new values.