[R] Extracting from data.frame

[William Dunlap]

Use
   df[1,,drop=FALSE]
if you want the output to be a data.frame,
no matter how many columns df has.

The effective default value for drop
is TRUE if the output has a single column.
This does not depend on whether or not
you subscripted rows or columns or both.

Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com  

> -----Original Message-----
> From: r-help-bounces at r-project.org 
> [mailto:r-help-bounces at r-project.org] On Behalf Of James Hirschorn
> Sent: Sunday, November 14, 2010 4:32 PM
> To: R-help at r-project.org
> Subject: [R] Extracting from data.frame
> 
> Can someone please explain the following behavior?
> 
>  
> 
> df1 and df2 are data.frames. Suppose I want a subset of the rows
> (observations) using extraction, say just the first row. What 
> I want to know
> is why if df1 has just one column then df1[1,] returns a 
> vector, whereas if
> df2 has 2 or more columns then df2[1,] returns a data frame? 
> Why is the
> single column case different?
> 
> 
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> 
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