[R] Graphic legend with mathematical symbol, numeric variable and character variable

["ECOTIÈRE David (Responsable d'activité) - CETE Est/LRPC de Strasbourg/6 Acoustique"]

Hi,

I'd like to make a legend with a mix of mathematical symbol (tau), 
numeric variable and character variables.I have tried :


types<-c("Type 1","Type 2","Type 2")
tau<-c(1,3,2)
legend(x="topright",legend=paste(types,"tau=",expression(tau)))



but it doesn't work: the 'tau' symbol is not written in its 'symbol 
style' but as 'tau'

Any (good) idea ?
Thank you in advance !

David