[R] How to make matrix missing data 0

[xin123620]

Dear All, 

I am trying to analysis traffic data with one timestamp column and speed
column. This data set contains six years data; for each year, I want to make
a matrix in (day of the year) * (hour)
         0  1  2   . . . 23
1    
2
.
.
365

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 to make a 366*24 table please? Any help is
appreciated.

Jessica


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