R help - May 2010 - Re : append new line in existing graph

Dear All,

I am executing my R script from PHP using the shell_exec.

$return = shell_exec("/usr/bin/R --slave --args
".$Domain.",".$Gender." <
/var/www/html/trends/newTrend.R");

In newTrend.R, I am plotting graph and save in pdf file using the below
code. It will create a pdf file with two line.

pdf(file="/var/www/html/trends/bmtrend.pdf", height=7.5, width=10.5)

g_range <- range(0,index , ReqDataindex)

plot(index, type="o", col="blue", ylim=g_range,axes=FALSE,
ann=FALSE)

axis(1, at=1:7, lab=c(1:daycount))

axis(2, las=1, at=25*0:g_range[2])

box()

lines(ReqDataindex, type="o", pch=22, lty=2, col="red")

Now what I want do is: I want to execute shell_exec() second time with
different argument  and I want to add one more line to existing
(bmtrend.pdf) file. I mean if the  bmtrend.pdf file does not exist, my
script has to create the file. If the bmtrend.pdf file is already exist, I
want to append new line in existing file.

any help would be greatly appreciated.

Thanks for you time.
Mohan L

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