Just wait until after you have the forecasts before you create the plot.
# Sample dates
xValues <- seq.Date(as.Date("1990-01-31"), to=as.Date("1992-12-31"),
by="month")
# Sample y value
yValues <- seq(0.1, length=length(xValues))
# Sample forecast one year from xValue's end point
fcastDate <- seq.Date(from=as.Date(xValues[length(xValues)]), length=2,
by="year")[2]
fcast <- 20
# The second forecast
fcastDate2 <- seq.Date(from=as.Date(fcastDate), length=2, by="year")[2]
fcast2 <- 15
plot(xValues, yValues, type="n", xlim=range(c(xValues, fcastDate,
fcastDate2)), ylim=range(c(yValues, fcast, fcast2)))
lines(xValues, yValues)
points(fcastDate, fcast, col="red")
points(fcastDate2, fcast2, col="blue")
Jean
-----
From: Jorgy Porgee <jorgy.porgee <at> gmail.com>
Subject: How do I plot a line followed by two forecast points?
Newsgroups: gmane.comp.lang.r.general
Date: 2009-08-07 15:17:52 GMT (2 hours and 55 minutes ago)
Good day all,
I'm trying to plot a continuous line plot, which is followed by two
forecast points eg. one forecast point is 12 months out, and another 24
months out from the last date of the line plot.
In my attempts so far, the second plot (the forecast points) is scaled
against a new axis scale, thus the two plots are not directly comparable
(I need the forecast points to be scaled according to the existing y
axis).
An example is pasted below. Any ideas on how to achieve this would be much
appreciated.
Thanking you in advance,
George.
# Sample dates
>xValues =
seq.Date(as.Date("1990-01-31"),to=as.Date("1992-12-31"),by="month");
# Sample y value
> yValues<-NULL;
> yValues[1:length(xValues)]=seq(0.1,length=length(xValues))
# Plot the series as a line
> plot(xValues,yValues,type="l");
# Sample forecast dates that start from xValue's data point
>
fcastDates=seq.Date(from=as.Date(xValues[length(xValues)]),length=12,by="month");
> fcastDates
[1] "1992-12-31" "1993-01-31" "1993-03-03" "1993-03-31" "1993-05-01"
"1993-05-31"
[7] "1993-07-01" "1993-07-31" "1993-08-31" "1993-10-01" "1993-10-31"
"1993-12-01"
# Sample forecast (we only want the forecast point to be displayed)
> fcast<-NULL; fcast[1:length(fcastDates)]="NA"; fcast[length(fcast)]<-20;
> fcast
[1] "NA" "NA" "NA" "NA" "NA" "NA" "NA" "NA" "NA" "NA" "NA" "20"
# Add the forecast plot to the original plot
> par(new=TRUE)
> plot(fcastDates,fcast,yaxt="n",xaxt="n",col="red")
Warning message:
In xy.coords(x, y, xlabel, ylabel, log) : NAs introduced by coercion
# The second forecast
>
fcastDates2=seq.Date(from=as.Date(fcastDates[length(fcastDates)]),length=12,by="month");
> fcastDates2
[1] "1993-12-01" "1994-01-01" "1994-02-01" "1994-03-01" "1994-04-01"
"1994-05-01"
[7] "1994-06-01" "1994-07-01" "1994-08-01" "1994-09-01" "1994-10-01"
"1994-11-01"
> fcast2<-NULL; fcast2[1:length(fcastDates2)]="NA";
fcast2[length(fcast2)]<-15;
> par(new=TRUE);plot(fcastDates2,fcast2,yaxt="n",xaxt="n",col="blue")
Warning message:
In xy.coords(x, y, xlabel, ylabel, log) : NAs introduced by coercion
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