Volcano Plot

Hi I am using the ggplot2 package for the volcano plot and I am using the
following code for the same:

g = ggplot(data=data, aes(x=data[11], y=-log10(data[12]), colour=threshold))
+
+   geom_point(alpha=0.4, size=1.75) +
+   opts(legend.position = "none") +
+   xlim(c(-10, 10)) + ylim(c(0, 15)) +
+   xlab("log2 fold change") + ylab("-log10 p-value")

data[11] is a column of the fold change values and data[12] contains the P
values and I am getting a following error:

Error: geom_point requires the following missing aesthetics: x, y
  What can be done for the same ?
And if not what other package may I use for the same in which I don't have
to use a lmfit model?

Thanks

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