[R] Question about levels/as.numeric

[Peter Ehlers]

Thibault,

Your questions indicate that you would benefit enormously
from reading 'An Introduction to R'.

A very useful function is str().
Understanding the concept of "factors" is crucial in R.

"Checking" anything with Excel is never much use.

Peter Ehlers

On 2011-04-10 08:47, Thibault Vatter wrote:
> Hi,
>
> I am still new to R and this is my first post on this mailing-list.
>
> I have two .csv (each one being a column of real numbers) coming from the
> same database (the first one is just longer than the second) and I read them
> in R the following way:
>
> returns<- read.csv("test.csv", header = FALSE)
> returns2<- read.csv("test2.csv", header = FALSE)
>
> However, the two objects clearly don't seem to be equivalent:
>
>> returns[2528:2537,1]
>   [1] -0.002206 0.115696  -0.015192 0.008719  -0.004654 -0.010688 0.009453
> 0.002676  0.001334  -0.011326
> 7470 Levels: -0.000078 -0.000085 -0.000086 -0.0001 -0.000112 -0.000115
> -0.000152 -0.000154 -0.000157 -0.00016 -0.000171 -0.000185 -0.000212
> -0.000238 -0.000256 -0.000259 -0.000263 -0.000273 ... C
>
>> returns2[1:10,1]
>   [1] -0.002206  0.115696 -0.015192  0.008719 -0.004654 -0.010688  0.009453
> 0.002676  0.001334 -0.011326
>
>> as.numeric(returns[2528:2537,1])
>   [1]  341 7444 2244 5149  787 1717 5251 4122 3878 1811
>
>> as.numeric(returns2[1:10,1])
>   [1] -0.002206  0.115696 -0.015192  0.008719 -0.004654 -0.010688  0.009453
> 0.002676  0.001334 -0.011326
>
> I would like to understand what's happening and how to handle the longer
> one. This problem may seem stupid, but I've been trying to figure it out for
> a while and nothing seems to work. I checked in excel and both seems to be
> completely normal lists of real numbers).
>
> What am I missing here? What are those "levels" and why the as.numeric
> doesn't work the same with the longer one?
>
> My final goal  is to extract small parts of those columns the following way:
>
>> cbind(returns[which(names == id)[2528:2537],1])
>        [,1]
>   [1,]  341
>   [2,] 7444
>   [3,] 2244
>   [4,] 5149
>   [5,]  787
>   [6,] 1717
>   [7,] 5251
>   [8,] 4122
>   [9,] 3878
> [10,] 1811
>
> Wich should be equivalent to:
>
>> cbind(returns2[which(names == id)[1:10],1])
>             [,1]
>   [1,] -0.002206
>   [2,]  0.115696
>   [3,] -0.015192
>   [4,]  0.008719
>   [5,] -0.004654
>   [6,] -0.010688
>   [7,]  0.009453
>   [8,]  0.002676
>   [9,]  0.001334
> [10,] -0.011326
>
> Thanks a lot,
> Thibault
>
> ---------
> *Thibault Vatter*
>   EPFL- Master, 1ère année
> Laboratory of Statistical Biophysics<http://lbs.epfl.ch/>
>
> Tel: +41 78 820 18 64
>   @: thibault.vatter at epfl.ch
> Web: http://personnes.epfl.ch/thibault.vatter
>
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