Problem having tick marks aligned when plotting three graphs on top of one another.

R 2.10
Windows 7

I am trying to plot three graphs on top of each other. I need to have the axises perfectly aligned. For some reason the ticks on the y axes are slightly off so they do not perfectly align. Can someone tell me how I can get the to overlay each other perfectly? I thought the yaxp parameter would solve my problem, but it does not. My data and code follows:

summaryresults[1:20,]

Slope PctCont PctCat PctTTst
 [1,]  0.05     7.4    5.6     6.3
 [2,]  0.10    17.7   11.3    13.3
 [3,]  0.15    32.7   18.7    25.6
 [4,]  0.20    53.3   27.5    40.2
 [5,]  0.25    72.1   41.2    54.5
 [6,]  0.30    85.5   52.9    70.8
 [7,]  0.35    93.9   65.2    83.6
 [8,]  0.40    97.0   73.6    89.9
 [9,]  0.45    99.7   84.8    96.5
[10,]  0.50    99.9   90.1    98.4
[11,]  0.55   100.0   93.2    99.7
[12,]  0.60   100.0   97.3    99.8
[13,]  0.65   100.0   98.8   100.0
[14,]  0.70   100.0   99.4   100.0
[15,]  0.75   100.0   99.8   100.0
[16,]  0.80   100.0   99.7   100.0
[17,]  0.85   100.0  100.0   100.0
[18,]  0.90   100.0  100.0   100.0
[19,]  0.95   100.0  100.0   100.0
[20,]  1.00   100.0  100.0   100.0

plot(summaryresults[,"Slope"],summaryresults[,"PctCont"],type="b",yaxp=c(0,100,10))
par(new=TRUE)
plot(summaryresults[,"Slope"],summaryresults[,"PctCat"],type="b",yaxp=c(0,100,10))
par(new=TRUE)
plot(summaryresults[,"Slope"],summaryresults[,"PctTTst"],type="b",yaxp=c(0,100,10))

John David 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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