R help - Oct 2011 - reshape2: Lost Values Between melt() and dcast()

Working with 5 subset streams from my source data frame, three of them
successfully call dcast(), but two fail:

jerritt.cast <- dcast(jerritt.melt, site + sampdate ~ param)
Aggregation function missing: defaulting to length

and

winters.cast <- dcast(winters.melt, site + sampdate ~ param)
Aggregation function missing: defaulting to length

   Yet both data frames have the values in their .melt data frames:

summary(jerritt.melt)
       site         sampdate              param       variable
  JCM-1  :2178   Min.   :1978-03-28   pH     : 292   quant:7519
  JCM-20A:2149   1st Qu.:1996-05-24   As     : 286
  JC-E   : 476   Median :2000-05-31   SO4    : 271
  JC     : 400   Mean   :2001-02-04   TDS    : 271
  GD-1   : 395   3rd Qu.:2006-05-31   Cl     : 253
  JC-2   : 349   Max.   :2009-12-30   Zn     : 250
  (Other):1572                        (Other):5896
      value
  Min.   :    0.000
  1st Qu.:    0.005
  Median :    0.650
  Mean   :  317.588
  3rd Qu.:   27.000
  Max.   :20450.000
  NA's   : 2134.000

and

summary(winters.melt)
       site        sampdate              param      variable
  WC     :601   Min.   :1987-07-23   As     : 96   quant:1189
  WC-2   :327   1st Qu.:1994-06-15   TDS    : 79
  WC-1   :261   Median :1995-07-27   NO3-N  : 74
  BC-0.5 :  0   Mean   :1997-05-15   pH     : 72
  BC-1   :  0   3rd Qu.:1996-07-29   SO4    : 69
  BC-1.5 :  0   Max.   :2011-06-06   Cl     : 64
  (Other):  0                        (Other):735
      value
  Min.   :   0.00
  1st Qu.:   0.05
  Median :   7.59
  Mean   :  79.20
  3rd Qu.:  75.00
  Max.   :2587.00
  NA's   : 252.00

   What might be causing dcast() to fail with these two data frames while it
succeeds with three others processed using the same syntax? If additional
information would help, let me know and I'll provide it.

Puzzled,

Rich

The reason dcast would give that warning (not a failure) is if the
formula you gave did not specify unique values.  Thus, dcast needs an
aggregating function, which defaults to length.

However, the dcast calls that "failed" can be helpful for determining
the source of your error.  I'd look at the outputs of those two dcast
calls and find cells where the length is > 1.  Those are duplicated
entries in your initial data.frames (when I've run into this is was
usually due to NA values somewhere unexpected).

Hope that clarifies things.

Justin


On Mon, Oct 31, 2011 at 9:32 AM, Rich Shepard <rshepard at
appl-ecosys.com> wrote:
> ?Working with 5 subset streams from my source data frame, three of them
> successfully call dcast(), but two fail:
>
> jerritt.cast <- dcast(jerritt.melt, site + sampdate ~ param)
> Aggregation function missing: defaulting to length
>
> and
>
> winters.cast <- dcast(winters.melt, site + sampdate ~ param)
> Aggregation function missing: defaulting to length
>
> ?Yet both data frames have the values in their .melt data frames:
>
> summary(jerritt.melt)
> ? ? ?site ? ? ? ? sampdate ? ? ? ? ? ? ?param ? ? ? variable
> ?JCM-1 ?:2178 ? Min. ? :1978-03-28 ? pH ? ? : 292 ? quant:7519
> ?JCM-20A:2149 ? 1st Qu.:1996-05-24 ? As ? ? : 286
> ?JC-E ? : 476 ? Median :2000-05-31 ? SO4 ? ?: 271
> ?JC ? ? : 400 ? Mean ? :2001-02-04 ? TDS ? ?: 271
> ?GD-1 ? : 395 ? 3rd Qu.:2006-05-31 ? Cl ? ? : 253
> ?JC-2 ? : 349 ? Max. ? :2009-12-30 ? Zn ? ? : 250
> ?(Other):1572 ? ? ? ? ? ? ? ? ? ? ? ?(Other):5896
> ? ? value
> ?Min. ? : ? ?0.000
> ?1st Qu.: ? ?0.005
> ?Median : ? ?0.650
> ?Mean ? : ?317.588
> ?3rd Qu.: ? 27.000
> ?Max. ? :20450.000
> ?NA's ? : 2134.000
>
> and
>
> summary(winters.melt)
> ? ? ?site ? ? ? ?sampdate ? ? ? ? ? ? ?param ? ? ?variable
> ?WC ? ? :601 ? Min. ? :1987-07-23 ? As ? ? : 96 ? quant:1189
> ?WC-2 ? :327 ? 1st Qu.:1994-06-15 ? TDS ? ?: 79
> ?WC-1 ? :261 ? Median :1995-07-27 ? NO3-N ?: 74
> ?BC-0.5 : ?0 ? Mean ? :1997-05-15 ? pH ? ? : 72
> ?BC-1 ? : ?0 ? 3rd Qu.:1996-07-29 ? SO4 ? ?: 69
> ?BC-1.5 : ?0 ? Max. ? :2011-06-06 ? Cl ? ? : 64
> ?(Other): ?0 ? ? ? ? ? ? ? ? ? ? ? ?(Other):735
> ? ? value
> ?Min. ? : ? 0.00
> ?1st Qu.: ? 0.05
> ?Median : ? 7.59
> ?Mean ? : ?79.20
> ?3rd Qu.: ?75.00
> ?Max. ? :2587.00
> ?NA's ? : 252.00
>
> ?What might be causing dcast() to fail with these two data frames while it
> succeeds with three others processed using the same syntax? If additional
> information would help, let me know and I'll provide it.
>
> Puzzled,
>
> Rich
>
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