Thanks  for the response. I proivded the necessary details below,  and also
have a general question for how to deal with dates in R. Is there a way to
make R read dates as numbers?

Here is the details of the R code:

egfr <- read.csv(file.choose(), header=TRUE, sep=",")   #egfr is a matrix
read from a .csv file.

egfr_value=egfr$VALUE  #a vector that contains all the values of y

test_egfr=egfr_value[1:14]  #a vector with the first 14 values of y

lab_date=egfr$LAB  #a vector that contains all the values of x, which are
dates

test_lab_date=lab_date[1:14] # a vector with the first 14 values of x

test_egfr
 [1] 16.8 16.9 20.4 16.8 19.5 20.2 17.2 17.8 15.9 15.6 17.3 15.3 17.4 15.9
666 Levels:  <5 0 10 10.1 10.2 10.3 10.4 10.5 10.6 10.7 10.8 10.9 ... There
is

> test_lab_date
 [1] 11/12/1999 11/29/1999 1/4/2000   1/14/2000  1/31/2000  2/8/2000
2/17/2000
 [8] 2/19/2000  2/22/2000  2/23/2000  2/4/1997   2/25/1997  3/11/1997
3/25/1997
3538 Levels:  1/1/2004 1/1/2005 1/1/2006 1/1/2007 1/1/2009 1/1/2010 ...
9/9/2010

R code:
> lm.egfr=lm(test_lab_date~test_egfr)


Error  messsage after running the above line:

Error in storage.mode(y) <- "double" :
  invalid to change the storage mode of a factor
In addition: Warning message:
In model.response(mf, "numeric") :
  using type="numeric" with a factor response will be ignored

Thanks,


On Mon, Dec 27, 2010 at 3:04 PM, Entropi ntrp <entropy053@gmail.com> wrote:

> Hi,
> I am trying to do simple linear regression using dates in R but receiving
> error messages. With the data shown below, I would like to regress x on y.
>
> x                                 y
>   11/12/1999 56.8  11/29/1999 17.9  01/04/2000 27.4  1/14/2000 96.8
> 1/31/2000 49.5
> R gives the following error messages  after reading the linear regression
> command:
>
>   Error in storage.mode(y) <- "double" :
>   invalid to change the storage mode of a factor
> In addition: Warning message:
> In model.response(mf, "numeric") :
>   using type="numeric" with a factor response will be ignored
>
> Can someone explain me how to resolve this issue?
>
> I appreciate your help in advance.
>
>
>
>
>
>

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