[R] tapply output as a dataframe

[Graves, Gregory]

On Mon, Apr 13, 2009 at 12:41 PM, Dan Dube <ddube-at-advisen.com> wrote:

> i use tapply and by often, but i always end up banging my head against
> the wall with the output.

The proposed solution of Dan's problem posted on R-help was: 

> do.call(rbind,a)

When I use this 'solution' I get 'ERROR:  second argument must be a list'.  So head on wall continues.

My tapply output is generated as follows:

> a=tapply(value,list(sampling.date,station.code),mean)

which gives me this (in part):

             A     B     C     D     E     F     G     H     I     J      K
1/15/2008  0.004 0.027 0.019 0.015 0.035 0.022 0.007 0.038 0.042 0.045 0.0350
1/15/2009  0.027 0.027 0.031 0.015 0.008 0.021 0.007 0.027 0.026 0.029 0.0210
1/15/2010  0.016 0.020 0.015 0.022 0.015 0.013 0.007 0.014 0.019 0.019 0.0180
10/15/2007 0.052 0.051 0.032 0.024 0.017 0.044 0.015 0.058 0.063 0.061 0.0640
10/15/2008 0.042 0.054 0.030 0.017 0.024 0.030 0.019 0.044 0.047 0.051 0.0390
10/15/2009 0.047 0.035 0.031 0.020 0.012 0.039 0.019 0.051 0.055 0.054 0.0350

The only way I can figure out how to resolve this, such that I can, for example, plot station "A" against date, is to export the tapply output as a csv, and then reimport.

Suggestions?  I couldn't find a solution to this likely SIMPLE problem in Crawley or multiple searches of R help.

Gregory A. Graves, Lead Scientist
Everglades REstoration COoordination and VERification (RECOVER) 
Wetland Watershed Sciences / Restoration Sciences Department
South Florida Water Management District
Phones:  DESK: 561 / 682 - 2429 
                   CELL:  561 / 719 - 8157