-roger
Robert Brown FM CEFAS wrote:
Hi there,
I'm running R 2.0.0 on Windows 95. I'm trying to coerce a column of factors within a data frame to numeric. This is not a problem with a vector, but I can't find a way to index a column within a data frame to achieve this. All the examples from 'An introduction to R', 'S-plus 6 programmers guide', etc, use simple vectors. I'm sure I'm missing something obvious but I can't find a way to change a single column in data frame. Ive tried several approaches: here is one
summary(test)
age yrclass weight year 1 :10 1992 :10 Min. :0.005333 Min. :1993 2 :10 1989 : 9 1st Qu.:0.221790 1st Qu.:1995 3 :10 1990 : 9 Median :0.413411 Median :1997 4 :10 1991 : 9 Mean :0.420119 Mean :1997 5 :10 1988 : 8 3rd Qu.:0.559819 3rd Qu.:2000 6 :10 1993 : 8 Max. :1.189000 Max. :2002 (Other):82 (Other):89
contents(test)
Data frame:test 142 observations and 4 variables Maximum # NAs:0
Levels Storage age 23 integer yrclass 28 integer weight double year double
+--------+---------------------------------------------------------------------+ |Variable|Levels | +--------+---------------------------------------------------------------------+ | age |0,1,10,11,12,13,14,15,16,18,19,2,20,21,24,25,3,4,5,6,7,8,9 | +--------+---------------------------------------------------------------------+ | yrclass|1969,1974,1975,1978,1979,1980,1981,1982,1983,1984,1985,1986,1987,1988| | |1989,1990,1991,1992,1993,1994,1995,1996,1997,1998,1999,2000,2001,2002| +--------+---------------------------------------------------------------------+
is(test$yrclass,"factor")
[1] TRUE
is(test$yrclass,"numeric")
[1] FALSE
as(test[,2],"numeric")
[1] 1 1 2 3 3 4 5 6 6 6 7 7 8 8 8 8 9 9 9 9 10 10 10 10 10 [26] 10 10 11 11 11 11 11 12 12 12 12 12 12 12 13 13 13 13 13 13 13 14 14 14 14 [51] 14 14 14 14 15 15 15 15 15 15 15 15 15 16 16 16 16 16 16 16 16 16 17 17 17 [76] 17 17 17 17 17 17 18 18 18 18 18 18 18 18 18 18 19 19 19 19 19 19 19 19 20 [101] 20 20 20 20 20 20 20 21 21 21 21 21 21 21 21 22 22 22 22 22 22 22 23 23 23 [126] 23 23 23 24 24 24 24 24 25 25 25 25 26 26 27 27 28
is(test$yrclass,"numeric")
[1] FALSE
Regards,
Robert Brown
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-- Roger D. Peng http://www.biostat.jhsph.edu/~rpeng/
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