1. Expand the range of the ENDPOINTS= option so that it includes the LSL and USL. For example:
href=57 73 endpoints=(0 to 75 by 5)
You can read about how to control bin locations in histograms by reading the article "Choosing bins for histograms."
2. SAS provides ODS graphics as a built-in feature of analytical procedures. The options that are surfaced through the procedure syntax are intended to cover about 95% of the typical use cases. For customized graphics, SAS also provided the SGPLOT procedure which enables you to exercise more control over the placement, layout, and attributes of graphical elements such as lines, fonts, and tick marks. If you want to customize a histogram down to the colors of lines and the location of tick marks, I suggest you look into the HISTOGRAM statement for the SGPLOT procedure, as well as other statements that I highlight below:
proc sgplot data=sashelp.cars;
histogram mpg_city / binwidth=10 binstart=5
SCALE=count DATALABEL=COUNT;
density mpg_city / type=normal;
density mpg_city / type=kernel;
refline 57 73 / axis=X label=("LSL" "USL") lineattrs=(color=green);
xaxis values=(0 to 80 by 10);
yaxis grid;
run;
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