R quantmod chart_Series: Title and Subtitle allignment

Question

I am having problems with aligning my subtitle in chart_Series. At present it is just writing over the top of the x axis. Also is it possible to switch off the text that is automatically written at the top of a chart_Series chart so I can replace it with my own

  library(quantmod)
  getSymbols("SPY", from="2013-01-01", to=Sys.Date())
  chart_Series(SPY)


  title("S&P Index", sub = "text1\n\text2\ntext3",
  cex.main = 2,   font.main= 4, col.main= "blue",
  cex.sub = 0.75, font.sub = 3, col.sub = "red")

I would be grateful for your help.

Answer 1

The 'quantmod' graphics are object-oriented. Data is stored in an environment (named 'Env') inside another environment (named whatever you name it, 'cspy' in this case). Special charting functions are stored with along with the data in a 'proto'-object. It is a more object-oriented approach than is used in either the S3 or S4 programming paradigms that are much more common in R. The 'proto'-package should be consulted for more details. After nosing around the code in chartSeries and the object it creates, I can get the labeling at the top to go away with this:

cspy <- chart_Series(SPY, name = NULL)
cspy$Env$actions[[4]] <- NULL
cspy

The 'quantmod' code has this:

    cs$Env$name <- name
    text.exp <- c(expression(text(1 - 1/3, 0.5, name, font = 2, 
        col = "#444444", offset = 0, cex = 1.1, pos = 4)), 
                  expression(text(NROW(xdata[xsubset]), 
        0.5, paste(start(xdata[xsubset]), end(xdata[xsubset]), 
            sep = " / "), col = 1, adj = c(0, 0), pos = 2)))
    cs$add(text.exp, env = cs$Env, expr = TRUE)

... but I wasn't able to figure out a name for that leaf so I looked at :

cspy$Env$actions

... and saw that the name and date-range were in the 4th item. so I just deleted it. (To get rid of only the name it is trivial: chart_Series(SPY, name = NULL). (I don't know if the location of that graphical item in the object will be consistent and I do not see a method for access that object-leaf, so this is possibly an unstable hack.)

To make room for the margin text (subtitle):

 png("out.png")
 myoma <- par("oma")
 myoma[1] <- 3
 par("oma" =myoma)
 cspy
 title("S&P Index",  cex.main = 2,  font.main= 4, col.main= "blue")
   mtext(text= "text1\ntext2\ntext3", side=1, cex = 0.75, font = 3, col = "red",line=7)
 dev.off()

Answer 2

I am not familiar with chart_Series plot from before. Normally I would have used the plotting parameter mar to increase the margin at the bottom of the plot, to make some more room for the sub-title. However, I didn't manage to increase the margin that way. Instead I had to use oma, to increase the outer margins of the plot. I added the sub-titles using mtext, instead of using the sub argument in title. You set the distance from the plot with line. The default chart_Series title is turned off by setting name = NULL. Please also note the 'Note' in ?chart_Series: "Highly experimental (read: alpha) use with caution.". Anyway,

par(oma = c(5, 0, 0, 0))
chart_Series(SPY, name = NULL)

title("S&P Index", cex.main = 2, font.main = 4, col.main = "blue")

mtext(text = "text1\n\text2\ntext3",
      side = 1, line = 9, cex = 0.75, font = 3, col = "red")