On May 2, 2010, at 11:22 AM, Mohan L wrote:
Your code has a different name for the sample object. And it would
be more informative if you offered str on "sample1".
This is the result of str on "sample1".
> str(sample1)
'data.frame': 35943 obs. of 17 variables:
$ stdate : Factor w/ 7 levels "01/11/09 00:00",..: 1 1 1 1 1 1
1 1 1 1 ...
So stdate is not a date variable but that is probably not your
problem since it looks like the time portion of your not-dates are
all "00:00". tapply can work with this information
snipped
$ Login : Factor w/ 419 levels ".00","1.00","10.00",..: 114
283 217 216 14 1 2 2 407 327 ...
So "Login" is not a numeric class variable. Read the FAQ about the
proper way to convert that variable to numeric without loosing
information.
The Login column contain all numeric values . I don't understand why
I need to convert that variable to numeric?
BECAUSE IT"S NOT NUMERIC.
I have no way to determining _why_ it is not numeric, but it simply
is ... not. Your input method turned it into a factor. Perhaps there
was one missing delimiter, or there was a stray character in one of
the entries in the file. Who knows. Why waste time arguing? Follow the
directions for fixing the problem. Once you do so, location of the
element causing the problem may become more clear, since then the non-
numeric coercible elements will get turned into "NA"'s or "NaN"'s.
login column contain data like this :
> sample$Login
[35881] .00 1.00 .00 1.00 .00 .00
1.00 2.00
[35889] 1.00 3.00 .00 .00 .00 1.00 .
00 32.00
[35897] 2.00 4.00 .00 17.00 3.00 1.00
12.00 .00
[35905] 8.00 .00 3.00 7.00 .00 17.00 .
00 4.00
[35913] 16.00 4.00 20.00 7.00 .00 22.00
18.00 1.00
[35921] 3.00 3.00 .00 .00 37.00 3.00
12.00 3.00
[35929] 2.00 11.00 .00 5.00 77.00 1.00
4.00 1.00
[35937] 9.00 18.00 3.00 3.00 4.00 14.00 2.00
Factor variables can have labels that look like numbers.
The mode of Login is numeric only :
So what?
> mode(factor(c("a", "v", "c")) )
[1] "numeric"
Modes are not the same as classes. Factors are represented internally
as integers.
> mode(sample$Login)
[1] "numeric"
>
And I am also using as.numeric(as.character(sample$Login), still it
has some warning and NA . I don't understand why this is happening.
could you explain?
I already did explain. You are bordering on magical thinking here.
Since the class of sample$Login is "factor", your fervent desire to
make it "numeric" will accomplish nothing useful.
--
David.
> avglog <- with(sample1, tapply(as.numeric(as.character(sample
$Login)), stdate, mean))
Warning message:
In tapply(as.numeric(as.character(sample$Login)), stdate, mean) :
NAs introduced by coercion
> avglog
01/11/09 00:00 02/11/09 00:00 03/11/09 00:00 04/11/09 00:00 05/11/09
00:00
22.04866 16.65358 NA 15.84970
16.58600
06/11/09 00:00 07/11/09 00:00
16.20743 18.52379
Thanks & Rg
Mohan L
David Winsemius, MD
West Hartford, CT
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