Add text to plot with facetted bar chart

Question

My question is related to this question. I want "2014" in the 4-year facet. I tried to repeat but my code doesn't give what I want.

Annotating text on individual facet in ggplot2

This is my data

structure(list(Rot = structure(c(1L, 1L, 1L, 1L, 1L, 1L, 1L, 
1L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 3L, 3L, 3L, 
3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L), .Label = c("2-year", 
"3-year", "4-year"), class = "factor"), Rot.Herb = structure(c(3L, 
3L, 4L, 4L, 13L, 13L, 14L, 14L, 5L, 5L, 6L, 6L, 9L, 9L, 10L, 
10L, 15L, 15L, 16L, 16L, 1L, 1L, 2L, 2L, 7L, 7L, 8L, 8L, 11L, 
11L, 12L, 12L, 17L, 17L, 18L, 18L), .Label = c("A4-conv", "A4-low", 
"C2-conv", "C2-low", "C3-conv", "C3-low", "C4-conv", "C4-low", 
"O3-conv", "O3-low", "O4-conv", "O4-low", "S2-conv", "S2-low", 
"S3-conv", "S3-low", "S4-conv", "S4-low"), class = "factor"), 
    variable = structure(c(1L, 2L, 1L, 2L, 1L, 2L, 1L, 2L, 1L, 
    2L, 1L, 2L, 1L, 2L, 1L, 2L, 1L, 2L, 1L, 2L, 1L, 2L, 1L, 2L, 
    1L, 2L, 1L, 2L, 1L, 2L, 1L, 2L, 1L, 2L, 1L, 2L), .Label = c("Diversity", 
    "Evenness"), class = "factor"), N = c(4, 4, 4, 4, 4, 4, 4, 
    4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 
    4, 4, 4, 4, 4, 4, 4, 4, 4, 4), value = c(0.78537789925, 0.613408315, 
    1.305194686, 0.79519430975, 0.4481728555, 0.30608817425, 
    1.20978861475, 0.8580643725, 0.92387324875, 0.630166121, 
    0.945954185, 0.561172324, 1.43952456275, 0.8616864655, 1.23679146725, 
    0.831737624, 1.033474108, 0.80689293925, 0.9910142125, 0.79342098075, 
    1.175512223, 0.6293940245, 0.981614832, 0.62342189825, 1.351710013, 
    0.805075937, 1.6598348325, 0.7983622545, 1.01606920875, 0.5751418795, 
    1.0500365255, 0.56408326225, 1.07162937725, 0.6756859865, 
    0.45699816625, 0.44444147325), sd = c(0.354077266902404, 
    0.208934910331856, 0.169501822767995, 0.0774319459391732, 
    0.737366460962239, 0.40697977697835, 0.494107033311986, 0.11906912863268, 
    0.491492768082854, 0.34236657107712, 0.219739438843007, 0.205905593411204, 
    0.319301583035043, 0.0696484379979274, 0.0563293598951725, 
    0.0978700910274188, 0.446850757364563, 0.175073468716825, 
    0.426859848850874, 0.180469101499932, 0.526842123835502, 
    0.200470277385505, 0.574885944755375, 0.27189545397305, 0.39621771945215, 
    0.150798258847229, 0.275863362594154, 0.111178397407429, 
    0.254811233135664, 0.158920851982914, 0.198698241334475, 
    0.0730606635175717, 0.717706309307313, 0.453776579066358, 
    0.574276936403411, 0.513758415496589), se = c(0.177038633451202, 
    0.104467455165928, 0.0847509113839974, 0.0387159729695866, 
    0.368683230481119, 0.203489888489175, 0.247053516655993, 
    0.0595345643163399, 0.245746384041427, 0.17118328553856, 
    0.109869719421504, 0.102952796705602, 0.159650791517521, 
    0.0348242189989637, 0.0281646799475863, 0.0489350455137094, 
    0.223425378682282, 0.0875367343584126, 0.213429924425437, 
    0.090234550749966, 0.263421061917751, 0.100235138692753, 
    0.287442972377688, 0.135947726986525, 0.198108859726075, 
    0.0753991294236146, 0.137931681297077, 0.0555891987037145, 
    0.127405616567832, 0.0794604259914568, 0.0993491206672376, 
    0.0365303317587859, 0.358853154653656, 0.226888289533179, 
    0.287138468201705, 0.256879207748294), ci = c(0.563415944919255, 
    0.332462066715199, 0.26971522480343, 0.123211505132525, 1.1733145846647, 
    0.647595643784969, 0.786234551289211, 0.189465554245211, 
    0.782074671929471, 0.544781614588516, 0.349654482635521, 
    0.327641747494367, 0.508080071600555, 0.110826207087643, 
    0.089632581638694, 0.155733154793995, 0.71103927089404, 0.278580956835532, 
    0.679229274424713, 0.287166612643164, 0.838323385234058, 
    0.318992946792351, 0.914771825423139, 0.432646341459985, 
    0.630470808679215, 0.23995368085579, 0.438960169525453, 0.176909640028318, 
    0.40546153371869, 0.252878539112781, 0.316173242000635, 0.116255819336536, 
    1.14203089616693, 0.722059798737006, 0.91380275723334, 0.817504285602766
    )), .Names = c("Rot", "Rot.Herb", "variable", "N", "value", 
"sd", "se", "ci"), row.names = c(NA, -36L), class = "data.frame")

and the code to graph

p <- ggplot(Shannon.long2, aes(x=Rot.Herb, y=value, fill=factor(variable)))+
  geom_bar(stat="identity", position="dodge")+
  scale_fill_brewer(palette = "Set1")+
  theme_bw() +
  theme(panel.grid.major=element_blank()) +
  facet_grid(~Rot, scales = "free_x", space="free_x")+
  theme(legend.title=element_blank(),legend.text=element_text(size=20),legend.position="top")+
  geom_errorbar(aes(ymin=value-se, ymax=value+se), size=0.5, width=.25,position=position_dodge(.9))+
  xlab("\nTreatment") +
  theme(axis.title = element_text(size=24,face="bold", vjust=4), axis.text.x = element_text(size=20,angle = 90, hjust = 1)) +
  ylab("Shannon's H' and E'") +
  theme(axis.title = element_text(size=24,face="bold", vjust=2), axis.text.y = element_text(size=20, color="black"))+
  theme(strip.text.x = element_text(colour = "black", size = 20), strip.background = element_rect(fill = "white"))

produced graph (please don't mind the "2014" on the y-axis).

New code to annotate 2014, with help from eipi10

 ann_text <- data.frame(x = "S4-conv",y = 1.75,lab = "2014", Rot.Herb=NA, 
value=NA, variable=NA, 
N=NA, sd=NA, se=NA, ci=NA, 
Rot = factor("4-year",levels = c("2-year","3-year","4-year")))

I got an error saying Error: Discrete value supplied to continuous scale after I run p + geom_text(data = ann_text,label = "2014"). Please see what have been wrong with my code and data format. Thanks.

Add `ann_text$Rot.Herb=NA` to your annotation data frame. Even though you're not using that column in `geom_text`, ggplot expects it to be there if that column is used for an aesthetic in the main call to ggplot. — eipi10, Jun 10 '16 at 18:13
Thank you for your help. Did you mean `ann_text <- data.frame(x = "S4-conv",y = 1.75,lab = "2014", Rot = factor("4-year",levels = c("2-year","3-year","4-year")), ann_text$Rot.Herb=NA)? I did that and got new error `Error in eval(expr, envir, enclos) : object 'value' not found` — Little Bee, Jun 10 '16 at 18:25
That's because you also use the column `value` in your initial ggplot call. So you need to add `ann_text$value=NA` to your new data frame as well. Every column that's used in your initial call to ggplot also needs to be in any data frames you introduce into the plot later. — eipi10, Jun 10 '16 at 18:29
I'm sorry. I haven't been able to make it yet. This is my full edited code with all the column names in `Shannon.long2`: `ann_text <- data.frame(x = "S4-conv",y = 1.75,lab = "2014", Rot.Herb=NA, value=NA, variable=NA, N=NA, sd=NA, se=NA, ci=NA, Rot = factor("4-year",levels = c("2-year","3-year","4-year")))` . I got new error `Error: Discrete value supplied to continuous scale` but I did transform `Rot` to factor though. — Little Bee, Jun 10 '16 at 18:33
I've reopened the question, pending resolution of whether there's something else going on besides the issue I've already raised. For now, please take the code in your comment and add it as an update to your question. — eipi10, Jun 10 '16 at 18:37

eipi10 · Accepted Answer · 2016-06-10T21:42:38.383

It turns out the issue is that when you include value=NA in ann_text it gets interpreted as logical (rather than numeric, which is its mode in Shannon.long2), causing the error because ggplot expects a numeric variable rather than a categorical one. Set value=NA_real_ (in addition to NA, R has class-specific missing value constants; see ?NA for more info) in ann_text to ensure value is interpreted as numeric and resolve the error. Or set value to any number, e.g., value=0.

In the example below, I've removed all of the theme and lab statements to shorten the code down to the essentials:

p = ggplot(Shannon.long2, aes(x=Rot.Herb, y=value, fill=factor(variable))) +
  geom_bar(stat="identity", position="dodge") +
  geom_errorbar(aes(ymin=value-se, ymax=value+se), size=0.5, width=.25,position=position_dodge(.9)) +
  facet_grid(~Rot, scales = "free_x", space="free_x")

ann_text <- data.frame(x = "S4-conv", y = 1.75, lab = "2014", Rot.Herb=NA, 
                       value=NA_real_, variable=NA)

p + geom_text(data = ann_text, aes(label=lab, x, y))

Note that you also need to feed x and y values to geom_text to provide the label location.

Another option would be to just use the same x and y variable names as in your original data frame, since ggplot already knows these names and has scaled the graph based on them. Now the only missing column we need to add is variable:

ann_text <- data.frame(Rot.Herb = "S4-conv", value = 1.75, lab = "2014", variable=NA)

p + geom_text(data = ann_text, aes(label=lab, Rot.Herb, value))

Thank you so much for your time investigating the problem. I really appreciate. — Little Bee, Jun 10 '16 at 23:48
I ended up using this set of code `ann_text <- data.frame(x= "C2-low", y = 1.75,lab = "2014", variable=NA_real_, Rot.Herb=NA, value=0, N=0, sd=0, se=0, ci=0, Rot = factor("2-year",levels = c("2-year","3-year","4-year"))) p + geom_text(data = ann_text, aes(label=lab, x, y), size=8)` — Little Bee, Jun 10 '16 at 23:55

Add text to plot with facetted bar chart

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