R help - Jul 2012 - reshape2 errors on data frame

I've successfully reformatted data frames from long to wide with reshape2,
but this time I'm getting errors that I want to understand and resolve.
Here's the data frame structure and the results of the melt() and dcast()
functions:

str(waterchem)
'data.frame':	128412 obs. of  8 variables:
  $ site    : Factor w/ 64 levels
"D-1","D-2","D-3",..: 1 1 1 1 1 1 1 ...
  $ sampdate: Date, format: "2007-12-12" "2007-12-12" ...
  $ preeq0  : logi  TRUE TRUE TRUE TRUE TRUE TRUE ...
  $ param   : Factor w/ 37 levels
"Ag","Al","Alk_tot",..: 1 2 8 17 3 4 ...
  $ quant   : num  0.005 0.106 1 231 231 0.011 0.001 0.002 0.001 100 ...
  $ ceneq1  : logi  TRUE FALSE TRUE FALSE FALSE FALSE ...
  $ floor   : num  0 0.106 0 231 231 0.011 0 0 0 100 ...
  $ ceiling : num  0.005 0.106 1 231 231 0.011 0.001 0.002 0.001 100
...
> chem.melt <- melt(waterchem, idvars = c('site',
'sampdate', 'preeq0', 'param', 'ceneq1',
'floor', 'ceiling'))
Using site, preeq0, param, ceneq1 as id variables
> chem.cast <- dcast(chem.melt, site + sampdate + preeq0 + ceneq1 + floor
+ ceiling ~ param)
Error in eval(expr, envir, enclos) : object 'sampdate' not found

   Because these data have some censored data there is the logical indicator
(ceneq1) to identify censored and uncensored values the the interval ends
(floor and ceiling) for multiply censored values. One factor of analytical
interest whether the sampdate is pre- or post-event; that uses the logical
indicator preeq0.

   Please point out where my melt() and dcast() syntax was incorrect. I will
provide more information if needed.

TIA,

Rich

It would be very helpful to have some sample data to play with.  str() shows the
structure of the data set but it is not the data.

Something like dput(head(100))  would probably be enough.



John Kane
Kingston ON Canada

> -----Original Message-----
> From: rshepard at appl-ecosys.com
> Sent: Thu, 5 Jul 2012 08:46:31 -0700 (PDT)
> To: r-help at r-project.org
> Subject: [R] reshape2 errors on data frame
> 
>    I've successfully reformatted data frames from long to wide with
> reshape2,
> but this time I'm getting errors that I want to understand and resolve.
> Here's the data frame structure and the results of the melt() and
dcast()
> functions:
> 
> str(waterchem)
> 'data.frame':	128412 obs. of  8 variables:
>   $ site    : Factor w/ 64 levels
"D-1","D-2","D-3",..: 1 1 1 1 1 1 1 ...
>   $ sampdate: Date, format: "2007-12-12" "2007-12-12"
...
>   $ preeq0  : logi  TRUE TRUE TRUE TRUE TRUE TRUE ...
>   $ param   : Factor w/ 37 levels
"Ag","Al","Alk_tot",..: 1 2 8 17 3 4
> ...
>   $ quant   : num  0.005 0.106 1 231 231 0.011 0.001 0.002 0.001 100 ...
>   $ ceneq1  : logi  TRUE FALSE TRUE FALSE FALSE FALSE ...
>   $ floor   : num  0 0.106 0 231 231 0.011 0 0 0 100 ...
>   $ ceiling : num  0.005 0.106 1 231 231 0.011 0.001 0.002 0.001 100 ...
>> chem.melt <- melt(waterchem, idvars = c('site',
'sampdate', 'preeq0',
>> 'param', 'ceneq1', 'floor', 'ceiling'))
> Using site, preeq0, param, ceneq1 as id variables
>> chem.cast <- dcast(chem.melt, site + sampdate + preeq0 + ceneq1 +
floor
>> + ceiling ~ param)
> Error in eval(expr, envir, enclos) : object 'sampdate' not found
> 
>    Because these data have some censored data there is the logical
> indicator
> (ceneq1) to identify censored and uncensored values the the interval ends
> (floor and ceiling) for multiply censored values. One factor of
> analytical
> interest whether the sampdate is pre- or post-event; that uses the
> logical
> indicator preeq0.
> 
>    Please point out where my melt() and dcast() syntax was incorrect. I
> will
> provide more information if needed.
> 
> TIA,
> 
> Rich
> 
> ______________________________________________
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> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
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