Problem with numeric variable

Well, you were right. When I check with str() or summary(),
the data frame appears as having a factor for that column.
However, if I ask is.factor(C2), I get FALSE, and if I ask
is.numeric(C2) I get TRUE. This seems strange.
So I decided to reimport the dataframe, this time with NA as
undefined values, and not ?. C2 was imported as a numeric
variable, as checked with str() and is.numeric(). But I still
get the indexes and not the values when I use C2 for any
purpose, just as happened before. How can this be possible?
All the other columns in the table behave properly.
The only difference I see between this columns ans the others
is that it contains NA values.

Thanks again,
Francisco Torreira




---- Original message ----

Date: Sun, 14 Aug 2005 10:11:15 +0100
From: Patrick Burns <pburns at pburns.seanet.com>
Subject: Re: [R] Problem with numeric variable
To: ftorrei2 at uiuc.edu

I think your problem is that you have a factor rather
than a numeric vector (even though you say you checked
with 'is.numeric').  Missing values should be represented
by 'NA' and not by '?' which is what makes me think you
have a factor.

Patrick Burns
patrick at burns-stat.com
+44 (0)20 8525 0696
http://www.burns-stat.com
(home of S Poetry and "A Guide for the Unwilling S User")

ftorrei2 at uiuc.edu wrote:

Hello all,

I posted a question some days ago without getting any answers,
perhaps, as one of you kindly pointed out, because the
question was not clearly stated. Let me reformulate it:
In a frame, a column named C2 represents a numeric variable
(checked with is.numeric(C2)). Some rows in the frame have an
undefined value for C2, represented in the table by a ? sign.
The remaining rows have numeric values with 2 decimals. For
example, row 10 has 43.70 for C2, while row 1 has ?. The
problem is that when I list C2 values (or when I try to plot
them, etc), these values are not the ones that appeared in the
table. Below are the first 3 lines of what I get when I list C2:

C2

[1] 43 47 96 62 87 55 1 98 121 1 1 1 67 1 112 1 93 44
[19] 85 569 52 110 126 95 92 60 36 383 373 298 274 406 208 175
293 306
[37] 305 172 134 115 94 84 104 99 64 271 269 310 268 359 443
248 204 345

These are not the correct values for C2, and I guess that they
are just row numbers. How can I get the correct C2 values
ready for analysis? Is this problem related to the fact that
some rows have a ? value for C2?

Thanks in advance,
Francisco Torreira
Francisco Torreira
Spanish, Italian and Portuguese
Univ. of Illinois at Urbana-Champaign
707 South Mathews Aven.
4031 FLB
Urbana, IL, 61801