adding a vertical line to a chartSeries graphic

Question

I hope this isn't redundant as I've googled extensively and still have not found an answer. I'm plotting intraday data and want to place a vertical line at a specific point in time. It seems I have to use the function addTA but it always plots below my graph in some weird empty white space. Here's some sample code and data. Thanks for any help.

Data:

date,value
29-DEC-2010:00:02:04.000,99.75
29-DEC-2010:00:03:44.000,99.7578125
29-DEC-2010:00:05:04.000,99.7578125
29-DEC-2010:00:07:53.000,99.7421875
29-DEC-2010:00:07:57.000,99.71875
29-DEC-2010:00:09:20.000,99.7421875
29-DEC-2010:00:11:04.000,99.75
29-DEC-2010:00:12:56.000,99.7421875
29-DEC-2010:00:13:05.000,99.7421875

Code:

#set up data
data    = read.csv("foo.csv")
values  = data[,2]
time    = c(strptime(data[,1],format="%d-%b-%Y:%H:%M:%S",tz="GMT"))
dataxts = xts(values, order.by=time,tzone="GMT")

# chart data
chartSeries(dataxts)
# add vertical line - this is where I have no clue what's going on.
addTA(xts(TRUE,as.POSIXlt("2010-12-29 00:11:00",tz="GMT"),on=1))

What ends up happening is that I get a vertical line where I want it, 2010-12-29 00:11:00, but it sits in a new section below the graph instead of overlaid on it. Any ideas?

Answer 1

You're passing on as an argument to xts, but you should be passing it to addTA.

I think you mean to be doing this:

addTA(xts(TRUE,as.POSIXlt("2010-12-29 00:11:00",tz="GMT")),on=1)

That said, it still doesn't work for me with your sample data. However, if what you had works with your real data except it puts the line in a new panel, then this should work and not open a new panel.

I have an addVLine function in my qmao package that is essentially the same thing.

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Edit

Aside from the typo with the parenthesis, the xts object also needs a column name in order for addTA to work (I think... at least in this case anyway). Also, you must give an x value that exists on your chart (i.e. 11:04, not 11:00)

colnames(dataxts) <- "x"
chartSeries(dataxts)
addTA(xts(TRUE,as.POSIXlt("2010-12-29 00:11:04",tz="GMT")),on=1, col='blue')
# or
# library(qmao)
# addVLine(index(dataxts[7]))

Edit 2

Perhaps a better approach is to use the addLines function

addLines(v=7)

Or, if you know the time, but don't know the row number, you could do this

addLines(v=which(index(dataxts) == as.POSIXlt("2010-12-29 00:11:04", tz="GMT")))

which gives