How to edit facet wrapped bar plots in R

Question

I have a graph here:

dframe1$row <- row.names(dframe1)
library(reshape2)
dframe2 <- melt(dframe1, id=c("Site", "row"))
ggplot(dframe2, aes(x=as.numeric(row), fill=Site, y=value)) + geom_bar(stat="identity") +       facet_wrap(~variable, scales="free")

Basically I would like to know how I can change the colours so that they are different for each site (represented in the legend), and if it is possible to label the x and y axes individually for each mini graph and to get rid of the as numeric line at the bottom.

Here is the dput() of my data:

structure(list(Site = c(2L, 2L, 2L, 2L, 3L, 3L, 3L, 3L, 3L, 4L, 
4L, 4L, 4L, 5L, 5L, 6L, 6L, 6L), weight = c(0.193, 0.249, 0.263, 
0.262, 0.419, 0.204, 0.311, 0.481, 0.326, 0.657, 0.347, 0.239, 
0.416, 0.31, 0.314, 0.277, 0.302, 0.403), cell.count = c(2530000, 
729000, 336000, 436000, 292000, 0, 2e+05, 6450000, 2e+05, 18700000, 
7430000, 9920000, 22700000, 21600000, 227000, 169000, 5e+05, 
283000), eleocyte = c(1270000, 17, 7.3, 264000, 0, 0, 2e+05, 
0, 2e+05, 2270000, 0, 9920000, 22700000, 442, 153000, 169000, 
5e+05, 283000), lambda.max = c(459L, 459L, 459L, 459L, 462L, 
462L, 462L, 462L, 462L, 465L, 465L, 465L, 465L, 490L, 490L, 475L, 
475L, 475L), avepb.ppm = c(390.2, 373.3, 340.13, 403.2, 248.53, 
206.7, 238.5, 190.6, 597.2, 206.8, 174.4, 186.3, 138.5, 269.55, 
58.1, 5.225, 4.02, 6.85), aveworm.pb.ppm = c(9.59, 9.446, 4.193, 
21.9, 1.66, 7.415, 13.11, 3.01, 51.5, 5.985, 4.705, 26.38, 2.38, 
4.44, 4.67, 0.11, 0.085, 0.096), aveworm.g = c(0.09125, 0.264, 
14.699, 0.2425, 0.4793, 0.051, 0.0635, 0.0465, 0.2645, 0.0559, 
0.0795, 0.05765, 0.0846, 0.457, 0.0625, 0.0535, 0.1576, 0.16)), .Names = c("Site", 
"weight", "cell.count", "eleocyte", "lambda.max", "avepb.ppm", 
"aveworm.pb.ppm", "aveworm.g"), class = "data.frame", row.names = c(NA, 
-18L))

Answer 1

To change the colors you need to tell ggplot that Site is a factor (as @user20650 pointed out in the comments).

You already have individual axes for the mini graphs because you specified scales = "free" in facet_wrap().

To get rid of the as.numeric(row) label at the bottom of your graph you can specify that you do not want text there with the theme() statement. You could also achieve this by adding a blank label with p <- p + xlab("") instead of the theme() line.

This code produces the following figure:

library(ggplot2)
p <- ggplot(dframe2, aes(x = as.numeric(row), fill = as.factor(Site), y = value))
p <- p + geom_bar(stat = "identity") + facet_wrap(~variable, scales = "free")
p <- p + scale_fill_discrete("Site")
p <- p + theme(axis.title.x = element_blank())
p

To change the labels of the facets you can change the levels of the variables in your data frame. See this answer. Similar to:

levels(dframe2$variable) <- c("Weight", "Cell Count", "Eleocyte", "Lambda",
                              "Average PPM", "Average PB PPM", "Average G")

If you use facet_grid instead of facet_wrap you can use a labeller function (in case you do not want to change your data frame). See also the discussion here.

The Cookbook for R site is also a good resource for faceting questions.