Re: [R] forecasting a time series

2012-01-20 Thread nhomeier
Hi Michael,

I think you're right, I should be looking for predict instead of 
forecast. I'm still fairly new to R so often don't know what to look 
for. As a simplified example (let's neglect the fourier terms):

fit = auto.arima(data)

but now I have data.latest, so I want to use the ARIMA terms from fit 
but with data.latest

I'll look into predicting, thank you


On 1/20/2012 1:35 AM, Michael Weylandt [via R] wrote:
 Can you clarify what exactly you mean by this?

 [N]ow [I] would like to use the last X values to predict tomorrow's
 weather. I'm at a loss. All the functions I've come across (like
 forecast()) use the series and then forecast from the end point.

 It sounds like a prediction to me.

 Anyways, I think most methods do allow new values for the
 independent variables: e.g., the newdata argument to most predict()
 methods and the xreg arguments to forecast::forecast(). Do you know
 which method you are using?

 Hope this helps,

 Michael

 On Wed, Jan 18, 2012 at 4:17 PM, nhomeier [hidden email] 
 /user/SendEmail.jtp?type=nodenode=4312525i=0 wrote:

  Couldn't find this in the archives. I'm fitting a series of historical
  weather-related data, but would like to use the latest values to 
 forecast.
  So let's say that I'm using 1970-2000 to fit a model (using fourier 
 terms
  and arima/auto.arima), but now would like to use the last X values to
  predict tomorrow's weather. I'm at a loss. All the functions I've come
  across (like forecast()) use the series and then forecast from the end
  point.
 
  Do I need to decompose the fit and write it out the long way? For 
 example,
  Tomorrow = fit$coef[1]*Yesterday + fit$coef[2]*BeforeYesterday + etc
 
  or is there a function that I'm not finding?
 
  Thank you,
  Nicole
 
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[R] forecasting a time series

2012-01-18 Thread nhomeier
Couldn't find this in the archives. I'm fitting a series of historical
weather-related data, but would like to use the latest values to forecast.
So let's say that I'm using 1970-2000 to fit a model (using fourier terms
and arima/auto.arima), but now would like to use the last X values to
predict tomorrow's weather. I'm at a loss. All the functions I've come
across (like forecast()) use the series and then forecast from the end
point. 

Do I need to decompose the fit and write it out the long way? For example, 
Tomorrow = fit$coef[1]*Yesterday + fit$coef[2]*BeforeYesterday + etc

or is there a function that I'm not finding?

Thank you,
Nicole

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[R] POT package return levels

2011-09-30 Thread nhomeier
This may be a simple misunderstanding on my part, but I need help
understanding what POT is plotting. I'm trying to analyze a few different
datasets. If my dataset covers 500 years, but I have 60 points above my
threshold, what should be plotted as the (empirical) return period for the
largest value? I would expect it to be 500 years. Why is it never close to
that? 

An example with real numbers, over 382 years, I have 52 points over my
selected threshold. So why is the return period for this largest point
coming out at 1200 years? Again, this is for the actual data. The model can
be whatever it, I don't care, but the data should at least be easy to
understand.

I'm using the POT package, and tasks fitgpd, plot, retlev (latter two with
npy=52/382).

Thanks in advance for any help.

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