r - Adding expressions to facet labeller in ggplot 2 2.0 -

i need replace 1 facet wrap label complicated expression. however, cannot function facet_wrap_labeller work anymore plots created under older ggplot2 versions.

        data <- as.data.frame(matrix(rnorm(60),20,3))          data$factor <- c(rep("f1", 4),rep("f2", 4), rep("f3", 4), rep("f4",4),rep("f5", 4))         names(data) <- c("a", "b", "c", "factor")         melted <- melt(data)          p <- ggplot(melted, aes(variable, value)) +              stat_boxplot(geom ='errorbar') +               geom_boxplot()         p1 <- p + facet_wrap(~factor)         facet_wrap_labeller(p1, labels=c("a", "b", expression({}^2*italic(d)~textstyle(group("(", rarefied, ")"))))) 

and get:

error in getgrob(gg[[strips[ii]]], "strip.text", grep = true, global = true) :    valid child "gtree" called from: getgrob(gg[[strips[ii]]], "strip.text", grep = true, global = true) 

i believe happening because of ggplot2 2.0 not being compatible function.

i tried labeller=labeller(), , labeller=bquote() arguments, when tried use vector

newlabels <- c(a="a", b="b",,     d=expression({}^0*italic(d)~textstyle(group("(", rarefied, ")")))) 

in

p1 <- p + facet_wrap(~factor,             labeller = labeller(factor=newlabels)) 

the expression ignored , original factor levels plotted. bquote, dont know add more 1 name argument.

any appreciated.

there appear 4 labels 5 facets in example, use labeller=label_parsed , rename factor levels easily, avoiding need function.

## rename levels (i used data.table::melt, characters) melted$factor <- factor(melted$factor,                          levels=paste0('f', 1:5),                         labels=c('a', 'b', 'c', '{}^0*italic(d)~plain((rarefied))', 'e'))  p <- ggplot(melted, aes(variable, value)) +   stat_boxplot(geom ='errorbar') +    geom_boxplot() p + facet_wrap(~factor, labeller=label_parsed)