[R] How do I plot a line followed by two forecast points?

[Jorgy Porgee]

Hi Jean,
Thank you for the reply. I do have the forecast points before I plot,
the example below was just for illustration purposes..If I am to add
the forecast points to one y-series data plot however, is there a way
of highlighting them? This is essentially what I'm trying to do below
by plotting 3 separate series on the same graph...
Any help would be much appreciated..

Regards,

George.
In addition, I can't add the forecasts to the original series because I need

On Fri, Aug 7, 2009 at 8:36 PM, Jean V Adams<jvadams at usgs.gov> wrote:
>
> 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