I have relatively easy question regarding the subsetting columns in R.
I have two data frames, dat1 and dat2:
>dat1
cities countries areakm2 populationk
1 Shanghai China 2643 21766
2 Beijing China 1368 21500
3 NYC USA Unknown 8406
4 LA USA 1302 3884
5 London UK 1737 Unknown
6 Manchester UK 116 255
> dat2
Ozone Solar.R Wind Temp Month Day
1 41 190 7.4 67 5 1
2 36 118 8.0 72 5 2
3 12 149 12.6 74 5 3
4 18 313 11.5 62 5 4
5 NA NA 14.3 56 5 5
Then, if I'd like to subset the first column from the dat1 I get the following:
> dat1[,1]
[1] Shanghai Beijing NYC LA London Manchester
Levels: Beijing LA London Manchester NYC Shanghai
> class(dat1[,1])
[1] "factor
However, if I do the same thing with dat2 I'll get a vector, not a factor.
> dat2[,1]
[1] 41 36 12 18 NA
> class(dat2[,1])
[1] "integer"
I can't understand what the difference is between these two cases. I assume that this is something to do with data types (in dat1 the first column consists of characters, while in dat2 of integers )
Thank you
Actualy both are vectors. One of factors and one of integers. If you want R to see them as characters (another type like factors or integers) you should use
stringsAsFactors = FALSE
In the creation of your data.frame