Arranging Views in Plotly R with Main Label - r

Question

Using the code snippet from the help page here, I'm trying to create a unique main label for each subplot but am not entirely successful. Any suggestions on how to do this?
library(plotly)
vars <- setdiff(names(economics), "date")
plots <- lapply(vars, function(var) {
plot_ly(economics, x = ~date, y = as.formula(paste0("~", var))) %>%
add_lines(name = var) %>% layout(title = paste("Title for", var, sep=' ') )
})
subplot(plots, nrows = length(plots), shareX = TRUE, titleX = FALSE)

Answer 1

I wish I had noticed this question sooner! Here is one way that you can make this happen.
I took the titles out of the plot build. Otherwise, you'll get an error.
library(plotly)
vars <- setdiff(names(economics), "date")
plots <- lapply(vars, function(var) {
plot_ly(economics, x = ~date, y = as.formula(paste0("~", var))) %>%
add_lines(name = var) #%>% layout(title = paste("Title for", var, sep=' '))
})
Then I created a vector of the titles.
nms <- invisible(lapply(vars, function(v){paste0("Title for ", v)}) %>% unlist())
Here I used annotations to create title objects to add to the subplot.
annots = lapply(
1:length(plots),
function(j){
list(x = .5,
y = 1 - (j - 1) * .205,
xanchor = "center",
yanchor = "center",
xref = "paper",
yref = "paper",
showarrow = F,
text = nms[j])
}
)
subplot(plots, nrows = length(plots), shareX = TRUE, titleX = FALSE) %>%
layout(annotations = annots)