I want to add text annotations over individual boxplots created using ggplot2. There are three variables. st for x axis, trt for grouping and yr for facet. The data and used is given below.
> dput(pans)
structure(list(trt = c("SP", "SP", "SP", "SP", "SP", "SP", "SP",
"OF", "OF", "OF", "OF", "OF", "OF", "OF", "CF", "CF", "CF", "CF",
"CF", "CF", "CF", "SP", "SP", "SP", "SP", "SP", "SP", "SP", "OF",
"OF", "OF", "OF", "OF", "OF", "OF", "CF", "CF", "CF", "CF", "CF",
"CF", "CF", "SP", "SP", "SP", "SP", "SP", "SP", "SP", "OF", "OF",
"OF", "OF", "OF", "OF", "OF", "CF", "CF", "CF", "CF", "CF", "CF",
"CF", "SP", "SP", "SP", "SP", "SP", "SP", "SP", "OF", "OF", "OF",
"OF", "OF", "OF", "OF", "CF", "CF", "CF", "CF", "CF", "CF", "CF"
), rep = c(1, 2, 3, 4, 5, 6, 7, 1, 2, 3, 4, 5, 6, 7, 1, 2, 3,
4, 5, 6, 7, 1, 2, 3, 4, 5, 6, 7, 1, 2, 3, 4, 5, 6, 7, 1, 2, 3,
4, 5, 6, 7, 1, 2, 3, 4, 5, 6, 7, 1, 2, 3, 4, 5, 6, 7, 1, 2, 3,
4, 5, 6, 7, 1, 2, 3, 4, 5, 6, 7, 1, 2, 3, 4, 5, 6, 7, 1, 2, 3,
4, 5, 6, 7), yr = c(2018, 2018, 2018, 2018, 2018, 2018, 2018,
2018, 2018, 2018, 2018, 2018, 2018, 2018, 2018, 2018, 2018, 2018,
2018, 2018, 2018, 2018, 2018, 2018, 2018, 2018, 2018, 2018, 2018,
2018, 2018, 2018, 2018, 2018, 2018, 2018, 2018, 2018, 2018, 2018,
2018, 2018, 2019, 2019, 2019, 2019, 2019, 2019, 2019, 2019, 2019,
2019, 2019, 2019, 2019, 2019, 2019, 2019, 2019, 2019, 2019, 2019,
2019, 2019, 2019, 2019, 2019, 2019, 2019, 2019, 2019, 2019, 2019,
2019, 2019, 2019, 2019, 2019, 2019, 2019, 2019, 2019, 2019, 2019
), st = c("b", "b", "b", "b", "b", "b", "b", "b", "b", "b", "b",
"b", "b", "b", "b", "b", "b", "b", "b", "b", "b", "h", "h", "h",
"h", "h", "h", "h", "h", "h", "h", "h", "h", "h", "h", "h", "h",
"h", "h", "h", "h", "h", "b", "b", "b", "b", "b", "b", "b", "b",
"b", "b", "b", "b", "b", "b", "b", "b", "b", "b", "b", "b", "b",
"h", "h", "h", "h", "h", "h", "h", "h", "h", "h", "h", "h", "h",
"h", "h", "h", "h", "h", "h", "h", "h"), act = c(39, 41, 45,
36, 33, 40, 41, 31, 28, 32, 36, 41, 30, 34, 30, 34, 25, 28, 27,
32, 27, 49, 42, 41, 48, 36, 46, 45, 33, 39, 41, 36, 32, 36, 39,
32, 33, 26, 27, 30, 31, 27, 43, 48, 42, 45, 41, 46, 44, 35, 31,
33, 29, 36, 33, 31, 25, 35, 24, 27, 28, 30, 26, 45, 50, 52, 47,
48, 50, 48, 31, 37, 33, 38, 35, 34, 36, 32, 28, 34, 26, 23, 30,
30)), class = c("spec_tbl_df", "tbl_df", "tbl", "data.frame"), row.names = c(NA,
-84L), spec = structure(list(cols = list(trt = structure(list(), class = c("collector_character",
"collector")), rep = structure(list(), class = c("collector_double",
"collector")), yr = structure(list(), class = c("collector_double",
"collector")), st = structure(list(), class = c("collector_character",
"collector")), act = structure(list(), class = c("collector_double",
"collector"))), default = structure(list(), class = c("collector_guess",
"collector")), skip = 1), class = "col_spec"))
rep <- factor(pans$rep)
trt <- factor(pans$trt)
yr <- factor(pans$yr)
st <- factor(pans$st)
p <- ggplot(pans, aes(x = st, y = act))
q<-p + geom_boxplot(aes(fill = trt), position = position_dodge(0.8)) +
stat_summary(fun = mean, geom = "point", shape=5, size=1.5,
aes(group = trt), position = position_dodge(0.8)) +
scale_fill_manual(name="System", values = c("grey50","grey90", "grey100")) +
facet_grid(. ~ yr)+
theme_bw()
plot<-q + scale_x_discrete(breaks=c("b","h"), labels=c("BS", "AH"))
plot2<-plot + theme(axis.title.x = element_blank())
plot2
The plotted chart
Then I tried adding annotation using geom_text using code (explained below). Got help from this link
pans2 = distinct(pans, yr, st, trt) %>%
arrange(yr, st, trt)
pans2$yloc = max(pans$act) + .05
pans2$label = c("a", "b", "a", "b", "b", "b", "a", "b", "a", "b", "b", "b")
plot2 + geom_text(data = pans2, aes(y = yloc, label = label),
position = position_dodge(width = .75))
However, I am getting the following error:
Don't know how to automatically pick scale for object of type function. Defaulting to continuous. Error: Aesthetics must be valid data columns. Problematic aesthetic(s): label = label. Did you mistype the name of a data column or forget to add after_stat()? Run rlang::last_error() to see where the error occurred.
Kindly help me in creating a graph with text annotations over each boxplot
question from:
https://stackoverflow.com/questions/65858612/how-to-add-text-annotation-over-each-boxplot-of-grouped-data-in-facet-grids-in-g 
