[R] Missing text in lattice key legend

[Luigi Marongiu]

Hello,
I am drawing some data with lattice using:
```
library(lattice)
COLS = c("gold", "forestgreen", "darkslategray3", "purple")
xyplot(Value ~ Concentration,
       group = Substance, data = inf_avg,
       pch = 16, cex = 1.2, type = "b",
       xlab=expression(bold(paste("Concentration (", mu, "M)"))),
       ylab=expression(bold("Infection rate")),
       col=COLS,
       scales = list(x = list(log = 10, at=c(unique(inf_avg$Concentration))
                              )
                     ),
       key = list(space="top", columns=4, col = "black",
                       points=list(pch=c(16, 16, 16, 16),
                                   col=COLS,
                                   text=list(c("6-PN", "8-PN", "IX", "XN")
                                            )
                                   )
                  ),
       panel = function(x,y) {
         panel.xyplot(x,y)
         errbar()
       }
)
```
It all works but the legend only shows the colored dots, there is no
text. Is it something missing from the syntax?
Thanks

-- 
Best regards,
Luigi