[R] How to make matrix missing data 0

David Winsemius dwinsemius at comcast.net
Thu Jul 7 22:38:28 CEST 2011

On Jul 7, 2011, at 3:52 PM, xin123620 wrote:

> Thank you William!!!! Your method does work!!!! I highly appreciate  
> that. :D
> Also thank you for replying, David. You are absolutely correct.  I  
> re-edited
> my posting to make question clear according to the guidelines in  
> case other
> person meet the similar problem as I have.
Copied from Nabble;
But you left it on Nabble which does not forward its updates to the  
list nor is an archival repository...it deletes things after an  
interval of a 12-18 months.  so here is what you should have included  
in this last posting:

Dear All,

I am trying to analysis six years traffic data with one timestamp  
column and one error flag column. I imported data through a postgre  
ODBC server.
qry<- paste("SELECT timestamp, error ORDER BY timestamp")
data<- sqlQuery(channel,qry)

The data is like so
               timestamp     error
2005-05-01 00:01:06    0
2005-05-01 00:02:46    2
2005-05-01 00:04:52    9
             .                    .
             .                    .
             .                    .

For the record, I formated timestamp in "day of year" and "hour"
             data$hour<- format(data$timestamp,'%H')
             data$doy<- format(data$timestamp,'%j')

For each year, I want to make a matrix in (day of the year) * (hour)  
which will be like so
          0  1  2   . . . 23

However random day's record is missing(e.g. there are 40 missing  
records in 2005 data set), when I tried to use tapply function, matrix  
came out is 326*23 table and there were no N/A remind me which day is  
missing data.

Can you give some hints please? Any help is appreciated.

> Thank you,
> Jessica
> --
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David Winsemius, MD
West Hartford, CT

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