Inserting dynamic most recent date in a plot (R)

Question

I gather the following data. In the plot, I would like to have a heading that says "most recent date: xxxx". (dynamic) Does anyone have a solution? Open for other ideas with similar outcome to show the most recent date on the plot.Thank you!

library(fImport)
library(zoo)
sentiment <- fredSeries("UMCSENT", from = "1995-01-04", to = "2017-01-01")
sp500 <- fredSeries("SP500", from = "1995-01-04", to = "2017-01-01")

plot(sentiment, type = "l", col = "Orange", ylab = "", xaxt = "n", 
     main = "Uni. Michigan Consumer Sentiment vs. SP500")
axis(2)
par(new = TRUE)
plot(sp500, , type = "l", col = "red", xaxt = "n", yaxt = "n", xlab = "Time", ylab = "")
axis(4)
mtext("SP500", side = 4, line = 3)
legend("bottomleft", col = c("Orange", "red"), lty = 1, 
       legend = c("Sentiment (Left)", "SP500 (Right)"))

Insert the most recent date (not working): (see comment section)

mtext(paste("Most Recent Data", 
      index(sentiment$UMCSENT)[dim(sentiment)[1]]), cex = 1, line = 0)

Answer 1

You can put the information in the sub title below the plot:

title(sub = paste("Most Recent Data", index(sentiment$UMCSENT)[dim(sentiment)[1]]))

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Update

After re-reading the comments, I think your issue is how to extract the date from your data. I am not familiar with timeSeries , but would

 title(sub = paste("Most Recent Data", tail(rownames(sentiment), 1)))

do the trick? Now you can decide whether you want to use mtext or title . This gives you the following plot:

Answer 2

If it is the date you want you need to look at the structure of sentiment

Time Series:          
Name:               object
Data Matrix:        
 Dimension:          255 1
 Column Names:       UMCSENT
 Row Names:          1995-02-01  ...  2016-04-01
Positions:          
 Start:              1995-02-01
 End:                2016-04-01
With:               
 Format:             %Y-%m-%d
 FinCenter:          GMT
 Units:              UMCSENT
 Title:              Time Series Object
 Documentation:      Mon May 23 09:59:47 2016

Here we see that the dates are within in the row.names of the object.

Thus add the following to your code to get the latest date

title(sub = paste("Most Recent Data", row.names(sentiment)[nrow(sentiment)]))