Robin,
You can use Lag (upper case "L") from package Hmisc.
Nestor Arguea
On Aug 18, 2008, at 8:40 AM, Williams, Robin wrote:
Dear all,
I am having difficulties using the seemingly-simple function lag.
I have a dataframe with several weather variables (maxitemp,
windspeed, rainfall etc), and the response variable (admissions). The
dataset is fairly large (1530 observations). I simply want to model
the
response against a lag of a couple of the explanatory variables, say
maxitemp and rainfall. I would like to look at lagtimes of 4 days,
i.e.
4 observations. My dataframe is called allengland.
I thought I would be able to do something like:
model1 <- lm(admissions~lag(maxitemp,4),data=allengland)
but when I compare this to a lag of 0 I have exactly the same output,
so I am clearly doing something wrong.
Could someone please point me in the right direction? The example in
the help for lag is not very detailed for what I need to do.
Thanks in advance,
Robin Williams
Met Office summer intern - Health Forecasting
[EMAIL PROTECTED]
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