Errata

where is 'sqrtn' defined? Is this supposed to be 'sqrt(n)'?

Note from the Author or Editor:
There is a missing opening parenthesis. Instead of `sqrtn)`, it should be `sqrt(n)`.

Old code:
ddply(cabbages, c("Cult", "Date"), summarise,
Weight = mean(HeadWt, na.rm=TRUE),
sd = sd(HeadWt, na.rm=TRUE),
n = sum(!is.na(HeadWt)),
se = sd / sqrtn) )

Corrected code:
ddply(cabbages, c("Cult", "Date"), summarise,
Weight = mean(HeadWt, na.rm=TRUE),
sd = sd(HeadWt, na.rm=TRUE),
n = sum(!is.na(HeadWt)),
se = sd / sqrt(n) )

In the sentence, "One method is to open the PDF graphics device with png()", the 'PDF' term should be replaced with 'PNG'.

Note from the Author or Editor:
The text contains "PDF", but it should be "PNG".

Old text:
"One method is to open the PDF graphics device with png() ..."

Corrected text:
"One method is to open the PNG graphics device with png() ..."

When the book was written, I bet it wasn't known that the next version would be 3.0, not 2.16 .

Note from the Author or Editor:
The text refers to R 2.16, but it should be R 3.0.

Instead of "This bug should be fixed in R 2.16", it should say "This bug was fixed as of R 3.0".

Figure 13-37 looks like a duplication of Fig 13-36. The Assault scale is still on a finely grained continuum, not the five cuts that I think was intended.

Note from the Author or Editor:
The image in Figure 13-37 is incorrect (the corrected version will appear in next printing).

In the sentence, "The first two rows of the data frame", I believe 'rows' should 'columns'

Note from the Author or Editor:
The text has "rows" where it should be "columns".

Old text:
"The first two rows of the data frame..."

Corrected text:
"The first two columns of the data frame..."

Since the default width of position_dodge() is NULL (see http://svitsrv25.epfl.ch/R-doc/library/ggplot2/html/position_dodge.html), the whole discussion section on this page is incorrect.

Note from the Author or Editor:
There's a simplification of how `width` works in `position_dodge()` which may be slightly confusing.


Old text:
To be more precise, the value of `width` in `position_dodge()` is the same as `width` in `geom_bar()`.

Corrected text:
To be more precise, the value of `width` in `position_dodge()` is `NULL`, which tells ggplot2 to use the same value as the `width` from `geom_bar()`.


(The text in backticks should be rendered as code in the output.)

The example relies on the map_data() routine. The text does not state that this routine is provided by the ggplot2 package and not the maps package. Therefore, the examples will not work if the ggplot2 library is not loaded.

Note from the Author or Editor:
The `map_data()` function is in ggplot2. The code is correct (since ggplot2 is assumed to be loaded for all the examples in the book), but to make it clear, a comment should be added to that line of code.

Old:
states_map <- map_data("state")

Corrected:
states_map <- map_data("state") # ggplot2 must be loaded to use map_data()

There is:
ddply(cabbage_exp, "Date", transform,
percent_weight = Weight / sum(Weight) * 100)

It should be (variable ce is used later in next code snippet):
ce <- ddply(cabbage_exp, "Date", transform,
percent_weight = Weight / sum(Weight) * 100)

Note from the Author or Editor:
The results of the ddply() command should have been saved in a variable `ce`, but they were not.

Original code:
ddply(cabbage_exp, "Date", transform,
percent_weight = Weight / sum(Weight) * 100)

Corrected code:
ce <- ddply(cabbage_exp, "Date", transform,
percent_weight = Weight / sum(Weight) * 100)

> ggplot(birthwt, aes(x=bwt)) + geom_histogram(fill="red"), colour="black"
Error: unexpected ',' in "ggplot(birthwt, aes(x=bwt)) + geom_histogram(fill="red"),"
>


Maybe, It should be
ggplot(birthwt, aes(x=bwt)) + geom_histogram(fill="red", colour="black")

Note from the Author or Editor:
A closing parenthesis is in the wrong place. The line that says:
ggplot(birthwt, aes(x=bwt)) + geom_histogram(fill="red"), colour="black"

should instead be:
ggplot(birthwt, aes(x=bwt)) + geom_histogram(fill="red", colour="black")

The three code snippets draws the graphs as expected, but also produce a message concerning stat="bin" and stat="identity". Possibly the the code snippets need stat="identity".

Note from the Author or Editor:
The code chunks for each plot should have stat="identity" added to each geom_bar():

ggplot(cabbage_exp, aes(x=Date, y=Weight, fill=Cultivar)) +
geom_bar(position="dodge", stat="identity")


ggplot(cabbage_exp, aes(x=Date, y=Weight, fill=Cultivar)) +
geom_bar(position="dodge", colour="black", stat="identity") +
scale_fill_brewer(palette="Pastel1")


ggplot(ce, aes(x=Date, y=Weight, fill=Cultivar)) +
geom_bar(position="dodge", colour="black", stat="identity") +
scale_fill_brewer(palette="Pastel1")