[R] Simple question about extracting a subset of data

rmailbox at justemail.net rmailbox at justemail.net
Mon Sep 29 21:59:19 CEST 2008

It's hard to read your table, but I think this could be your problem:
daylength = "long.day"  is always TRUE
Testing for equality uses "==" so
daylength == "long.day" may or may not always be TRUE

----- Original message -----
From: "Josh B" <joshb41 at yahoo.com>
To: "R Help" <r-help at r-project.org>
Date: Mon, 29 Sep 2008 12:54:59 -0700 (PDT)
Subject: [R] Simple question about extracting a subset of data

Hello all,

I have a (hopefully) simple question.

If I have a data table (named "x") such as this:

LD1.0222946-0.9697459 -0.60141837
SD -1.5892393-0.70540660.66469785
SD -0.5222961-0.7054066-0.10701187

How do create a new data table that contains, e.g., only the long-day plants?

I have tried to do this using the "subset" command, but it seems to ignore me:

x.sd <- subset(x, daylength = "long.day", select = root.weight:stem.diameter)

This returns exactly the same data table I had before (including both long and short day plants).

So how do I do this properly? Actual code would be of the most direct help to me, since I am new at this. Thank you very much!

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