[R] SQL Changing Data Type

GL pflugg at shands.ufl.edu
Fri Jun 24 22:12:35 CEST 2011


Passing in two dates to a sql statement (sqldf). Is returning a factor. Tried
setting back to a Date via as.Date, but get an error the error: character
string is not in a standard unambiguous format. Any thoughts appreciated. 

Code/Results listed below:

> summary(df.possible.combos)
      Date                 Hour      
 Min.   :2011-03-01   Min.   : 0.00  
 1st Qu.:2011-03-23   1st Qu.: 5.75  
 Median :2011-04-14   Median :11.50  
 Mean   :2011-04-14   Mean   :11.50  
 3rd Qu.:2011-05-06   3rd Qu.:17.25  
 Max.   :2011-05-31   Max.   :23.00  
> summary(df.aggregate)   
      Date                 Hour           x         
 Min.   :2011-03-01   16     : 82   Min.   : 1.000  
 1st Qu.:2011-03-22   17     : 82   1st Qu.: 1.000  
 Median :2011-04-13   18     : 82   Median : 2.000  
 Mean   :2011-04-14   19     : 79   Mean   : 4.195  
 3rd Qu.:2011-05-07   20     : 76   3rd Qu.: 7.000  
 Max.   :2011-05-31   7      : 75   Max.   :20.000  
                      (Other):377                   
> #merge raw data and all possible combinations
>   df.final <- sqldf('select Date, Hour, x as RoomsInUse from
> "df.aggregate"
+     left join "df.possible.combos" using (Hour, Date)')
> summary(df.final)
      Date          Hour       RoomsInUse    
 15069.0: 16   16     : 82   Min.   : 1.000  
 15114.0: 16   17     : 82   1st Qu.: 1.000  
 15063.0: 15   18     : 82   Median : 2.000  
 15082.0: 15   19     : 79   Mean   : 4.195  
 15125.0: 15   20     : 76   3rd Qu.: 7.000  
 15044.0: 14   7      : 75   Max.   :20.000  
 (Other):762   (Other):377                   
> thedate <- as.Date(df.final$Date)
Error in charToDate(x) : 
  character string is not in a standard unambiguous format
> 


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