Hi, 
  Please could someone explain how this element of predict.lm works?
From the help file 
`
newdata	  
An optional data frame in which to look for variables with which to
predict. If omitted, the fitted values are used.
' 
  Does this dataframe (newdata) need to have the same variable names as
was used in the original data frame used to fit the model? Or will R
just look across consecutive columns of newdata, and apply them to the
call as appropriate?
  For example, if I have fitted a model with four variables
(x1,x2,x3,x4) in my original dataframe, and then have a second dataframe
which I want to supply to the newdata argument in predict.lm with
variable names (x5, x6, x7, x8), do I need to change the variable names
in my newdata dataframe to match those of the original dataframe? Or
will R treat x5 as x1, x6 as x2, etc, when using predict.lm? 
  I would like to know so that I can design the structure of some
somewhat larger dataframes in a manner which will make using predict.lm
straight forward and quick.
Hope this makes sense.
Many thanks for any help. 
   Robin Williams
Met Office summer intern - Health Forecasting
robin.williams@metoffice.gov.uk 
 

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