R help - Oct 2007 - controlling plot range

Windows XP 
R 2.5.0
I am trying to produce two plots that have the same range, i.e. x from 50 to 400
on both plots and y from 50 to 400 on both plots. (This will allow me to compare
slopes). I have used the code below without success using usr (I have also used
xaxp and yaxp but I am not including the code):

plot(tgNo26[,"TGh"],tgNo26[,"TGs"],usr=c(50,400,50,400))
plot(tgNo26[grep("CONTROL",tgNo26[,"PATIENT"]),"TGh"],
    
tgNo26[grep("CONTROL",tgNo26[,"PATIENT"]),"TGs"],usr=c(50,400,50,400))

RESULT:
axes on first plot 50-400, y axis 50-350
axes on second plot 50-250 y axis 100-250


What am I doing wrong?

Thanks,
John

John Sorkin M.D., Ph.D.
Chief, Biostatistics and Informatics
University of Maryland School of Medicine Division of Gerontology
Baltimore VA Medical Center
10 North Greene Street
GRECC (BT/18/GR)
Baltimore, MD 21201-1524
(Phone) 410-605-7119
(Fax) 410-605-7913 (Please call phone number above prior to faxing)

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On Oct 19, 2007, at 10:54 AM, John Sorkin wrote:
> Windows XP
> R 2.5.0
> I am trying to produce two plots that have the same range, i.e. x  
> from 50 to 400 on both plots and y from 50 to 400 on both plots.  
> (This will allow me to compare slopes). I have used the code below  
> without success using usr (I have also used xaxp and yaxp but I am  
> not including the code):
>
>
plot(tgNo26[,"TGh"],tgNo26[,"TGs"],usr=c(50,400,50,400))
>
plot(tgNo26[grep("CONTROL",tgNo26[,"PATIENT"]),"TGh"],
>     
tgNo26[grep("CONTROL",tgNo26[,"PATIENT"]),"TGs"],usr=c
> (50,400,50,400))
>
> RESULT:
> axes on first plot 50-400, y axis 50-350
> axes on second plot 50-250 y axis 100-250
From

?plot.default

Are you looking for:

xlim		the x limits (x1, x2) of the plot. Note that x1 > x2 is allowed  
and leads to a ?reversed axis?.
ylim		the y limits of the plot.

I believe this will allow you to set the axes to the same limits so  
that you can compare more easily.

HTH

James