[R] as.Date from data.frame

[Marc Schwartz]

On Nov 11, 2009, at 12:06 PM, separent wrote:

>
> #Hello,
>
> #I loaded data using read.table - I needed to convert a row in the  
> data
> frame to date class:
>
>> data
>
> V1          V2          V3          V4
> 1  2008-05-19  2008-04-19  2008-03-21  2008-02-22
> 2 38.16999817 30.70999908 36.86000061 35.18999863
> 3 37.47999954 29.95000076 36.45999908 35.36000061
> 4 37.47999954 30.14999962 36.47000122 35.36000061
> 5 37.84999847 30.56999969 36.84000015 35.74000168
> 6 38.38999939 31.14999962 37.34000015 36.27000046
> 7 39.11000061 31.90999985 38.02999878 36.97999954
> 8 39.81000137 32.65000153 38.68000031 37.63999939
> 9 40.47000122 33.34999847 39.27999878 38.27000046
>
>> data[1,]
>          V1         V2         V3         V4
> 1 2008-05-19 2008-04-19 2008-03-21 2008-02-22
>
>> dates1<-as.Date(data[1,])
>
> do not know how to convert 'dates[1,]' to class "Date"
>
> # However, I can individually convert them all:
>
>> dates1.1<-as.Date(data[1,1])
>
>> dates1.1
> [1] "2008-05-19"
>
> # How can I change the class of the date over the entire row (my  
> original
> file contains more than one hundred rows)?
> # Thank you very much.

In a data frame, you cannot change the data type for a row, without  
changing the data type for the entire column.

That being said, it looks to me like each column contains continuous  
data for a chronological series.

If that is correct, then you want the dates to be the column names and  
not the first row., Thus, when you used read.table(), you should have  
included the argument 'header = TRUE', which would do just that. With  
read.table(), header is FALSE by default.

HTH,

Marc Schwartz