Question

I have the following data frame

id datestamp hrofday val1 val2 val3
a  20120401 0 3.2 0 1
a  20120401 1 3.3 4 0
a  20120401 2 3.4 6 0
...
a  20120401 23 7.3 0 2

It represents a user-id followed by hour of day, val1 val2 & val3.
I want to use cast to put the data frame in the following shape using either reshape or base R. For every id I want the values in val1 in each of the 24 fields and simultaneously find the total for val2 & val3. e.g. shown below

id datestamp val1.0 val1.1 val1.2 ... val1.23 total.val2 total.val3
a  20120401 3.2 3.3 3.4 ... 7.3 10 3
...

Any help much appreciated. Thanks in advance.

Answer 1

Not precisely what you wanted (slightly different column names):

vecs <-  by(dfrm, dfrm$id, FUN= function(dfr) 
return(data.frame(id = dfr$id[1], val1=matrix(dfr$val1, ncol=24), 
                   total.val2=sum(dfr$val2), total.val3=sum(dfr$val3) ) )
         )  

dfvecs <- do.call(rbind, vecs) # Not really needed for single group 
                       # .. but it is the standard way to recombine by() results

> dfvecs
  id val1.1 val1.2 val1.3 val1.4 val1.5 val1.6 val1.7 val1.8 val1.9 val1.10 val1.11
a  a   6.94   5.45   2.83   9.23   2.92   8.37   2.86   2.67   1.87    2.32    3.17
  val1.12 val1.13 val1.14 val1.15 val1.16 val1.17 val1.18 val1.19 val1.20 val1.21
a    3.03    1.59     0.4    2.19    8.11    5.26    9.15    8.31    0.46    4.56
  val1.22 val1.23 val1.24 total.val2 total.val3
a    2.65    3.05    5.07     118.44      99.02