[R] How to use different title in a loop

[Xinxin Yu]

Hi all,

I want to draw n plots whose titles are "Main effect of X_i", i= 1,  
2, ..., n, respectively.

More specifically, I use:

par(mfrow = c(n/2, 2))
for ( i in 1:n)
{
	plot(1:J, y[i, 1: J], main = 'Main effect of X_i')
}

This gives me a series of plots with the common title with a letter i  
in it, not the consecutive numbers I want.

Thanks in advance.

Xinxin