remove time gaps from dygraph financial data display

app.R

# dygraph workaround: how to avoid time gaps in financial data display
# Please add your voice for a permanent fix in the following thread:
#   https://github.com/rstudio/dygraphs/issues/70
# TODO:  date+time "2017-01-25 09:00:00" - looks like the JS environment can't deal with this format !?

library(shiny)
library(dygraphs)

ui <- fluidPage(
	titlePanel("Dygraph stock data"),
	mainPanel(
		checkboxInput('withGaps', 'show the data gaps', value=FALSE),
		dygraphOutput("testPlot")
	)
)

server <- function(input, output) {

	# library(quantmod)  # xts data
	# dtraw <- getSymbols('QCOM', from=Sys.Date()-40, auto.assign=FALSE)
	# dtraw <- OHLC(dtraw)
	# colnames(dtraw) <- c('open','high','low','close')
	# alld <- paste(as.Date(index(dtraw)), collapse="'),new Date('" )
	
	require(xts)
	data(sample_matrix)  # matrix data
	mid <- nrow(sample_matrix)/2
	dtraw <- rbind(head(sample_matrix,20), sample_matrix[(mid-20):(mid+20),], tail(sample_matrix,20)) # make 2 gaps
	alld <- paste(as.Date(rownames(dtraw)), collapse="'),new Date('" )	# collect the dates
	
	output$testPlot <- renderDygraph({

		if(input$withGaps)	# original display with gaps
			out <- dygraph(dtraw) %>% dyCandlestick()
		else {					# no gaps
			jsdates <- paste0("var d=[new Date('",alld,"')];")	# dates as JS array
			vformatter <- paste("function(v) {",jsdates,"return d[v-1].toLocaleDateString() }")
			aformatter <- paste("function(a) {",jsdates,"return (d[a-1] ? d[a-1].toDateString().slice(4,10) : null) }")
			rownames(dtraw) <- NULL    # for matrix data only
			# now that the date-display is ready, build new dataframe with sequential numbers instead of dates
			data <- data.frame(1:nrow(dtraw), coredata(dtraw))
			
			out <- dygraph(data) %>% dyCandlestick() %>%
				dyAxis("x", 
						 valueFormatter = vformatter,
						 axisLabelFormatter = aformatter
				)
		}
		out
	})
}
shinyApp(ui = ui, server = server)