Message-ID: <OFAE1707D9.DF900E7E-ONC1257920.004C000F-C1257920.004C3762@precheza.cz>
Date: 2011-10-05T13:54:52Z
From: PIKAL Petr
Subject: How to subset() from data frame using specific rows
In-Reply-To: <alpine.LNX.2.00.1110050554020.25250@salmo.appl-ecosys.com>
Hi
>
> On Wed, 5 Oct 2011, Petr PIKAL wrote:
>
> > Hm. I seldom use such approach. In your original request you said you
want
> > split your data to smaller data frames based on sites
>
> Petr,
>
> I need the additional information in the database, too.
But you do not loose them, your data frame is cut according to sites
variable and put into a list
see
> iris.spl<- split(iris, iris$Species)
> str(iris.spl)
List of 3
$ setosa :'data.frame': 50 obs. of 5 variables:
..$ Sepal.Length: num [1:50] 5.1 4.9 4.7 4.6 5 5.4 4.6 5 4.4 4.9 ...
..$ Sepal.Width : num [1:50] 3.5 3 3.2 3.1 3.6 3.9 3.4 3.4 2.9 3.1 ...
>
> > From what we know it is difficult to say if there is some common
feature
> > in site variable. If it is organised like
> > XY-N
> > you can simply make new variable from first two letters
>
> Unfortunately, the site designations are not so uniform. As I went
through
> the process of re-doing the data I discovered this lack of consistency
> resulting in duplicate records because one site had been designated XX-n
and
> XXn. Had to clean those up, too.
>
> > sites <- substr(chemdata$site,1,2)
Which would not matter if the first two letters designates required
grouping variable I called sites
Regards
Petr
> >
> > then you can split your data frame according to sites
> >
> > chem.spl <- split(chemdata, sites)
> >
> > and do anything with your splitted data frames organised in list
>
> First thing this morning I'm upgrading to 2.13.2 and hoping that this
> fixes an issue that just showed up yesterday afternoon: not being able
to
> access function help pages. For example, I tried ?subset and ?split
because
> I thought the latter is really what I want, yet R told me no help was
found.
> Strange; it was there a week ago.
>
> Thanks,
>
> Rich
>
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