Plotly markers to appear in a bar chart - r

Question

I am new to plotly and want to make my own bullet chart (a bit like http://bl.ocks.org/mbostock/4061961) that has markers/traces to show the values of the relevant values when comparing actual vs expected.
Below is my attempt:
q <- ggplot(data.frame(measure='',actual=25),aes(x=measure,y=actual))+
geom_bar(stat='identity')+
ylim(c(0,35))+
geom_hline(yintercept = 30,color='red')+
geom_text(y=30,label='Expected',angle=270,vjust=0)+
coord_flip()+
ylab('Num. of carrots')
q
q1 <- ggplotly(q) %>% add_markers()
q1
When converting it to plotly using ggplotly, the text looks like it has not rotated correctly, and the markers/traces do not show for the bar chart...Any help here would be much appreciated.
Kindest regards,
HLM

Answer 1

I do not think that plotly supports rotating text for type="scatter" (which is how ggplotly is interpreting your geom_text). You can delete the geom_text line from the ggplot graph, then add text to the plotly one using annotations:
q1 <- ggplotly(q) %>% add_markers() %>%
layout(annotations = list(x = 30, y = 1, text = "Expected", textangle=270))
q1
update
The 2nd part of your question (how to also get hover info on the bar) is slightly trickier. To get the hover info, we can create the bars using the plotly API directly like this
p.bars = plot_ly(data = data.frame(measure='', actual=25)) %>%
add_bars(y=~measure, x=~actual, orientation="h")
we can add the text annotation to it like this
p.bars.text = p.bars %>%
layout(annotations = list(x = 30, y = 0, text = "Expected", textangle=270,
showarrow=F, xanchor="center"))
But the problem is that adding a line also to this plot by
p.bars.text %>% add_segments(x=30, xend=30, y=-0.5, yend=0.5)
gives an error
Error in populate_categorical_axes(p) : Can't display both discrete & non-discrete data on same axis
I.e. we can only specify the y values of the line with respect to categorical values of y. So, for example we can do
dat1 = data.frame(measure=letters[1:2], actual=c(25,20))
plot_ly(data = dat1) %>%
add_bars(y=~measure, x=~actual, orientation="h") %>%
layout(annotations = list(x = 29, y = 0, text = "Expected", textangle=270,
showarrow=F, xanchor="center")) %>%
add_segments(x=30, xend=30, y='a', yend='b')
which gives the following in which the line is aligned with the category labels rather than with the width of the bars
The only solution I have to this at the moment is to use a numeric axis for the categories, and then set the axis labels using ticktext:
plot_ly(data = data.frame(measure=c(0,1), actual=c(25,20))) %>%
add_bars(y=~measure, x=~actual, orientation="h", showlegend=F) %>%
add_segments(x=30, xend=30, y=-0.4, yend=0.4, showlegend=F) %>%
layout(annotations = list(x = 29.5, y = 0, text = "Expected", textangle=270, showarrow=F, xanchor="center"),
yaxis = list(tickmode="array", tickvals=c(0,1), ticktext=c("", "") ))