[R] using the function "expression" with "paste" in a plot

[Ahmad Abu Hammour]

Hi,
I noticed that paste and expression in the following manner does not produce
the desired result.

vnames=c("pi","y","delta")
vx=vn=3
m=16
# mydata any matrix that takes for the following form
mydata=array(somedata,c(m,vn,vx))
# producing plots
for (j in 1:vx){
for (i in 1:vn)
{
plot(mydata, type="l", main=expression(paste("Effect of",
vnames[j],"on",vnames[i])), xlab="Lags (quarters)", ylab="Response")
}
}

The title appears as "Effect of vnamesj on vnamesi". Without the function
"expression" title for j=1 and i=2 appears as "Effect of pi on y". The
desired outcome would be return the word "pi" rather than a Greek letter.

Is there any simple way to overcome this situation.

Thank you
Ahmad Abu Hammour
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