On Dec 27, 2010, at 8:56 PM, Entropi ntrp wrote:
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.
Well, whatever file you chose might have been a matrix in its former
life, but is _now_ a dataframe.
egfr_value=egfr$VALUE #a vector that contains all the values of y
If egfr has a column named "VALUE" then that might be so. But what is
this "y-value" notion you are carrying on about?
test_egfr=egfr_value[1:14] #a vector with the first 14 values of y
1st 14 values of egfr_value, anyway.
lab_date=egfr$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
Of unceratin class at the moment.
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
Aha! A factor classed variable! .... not the numeric value you were
expecting. Your dataset had a non-numeric value and R decided it was
really a string during the process of read.csv() and made it a
factor. Look at the read.table help page and read about asIs and
stringsAsFactors.
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 <entropy...@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.
--
David Winsemius, MD
West Hartford, CT
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