[R] comparing fields within a record

[David Winsemius]

On Dec 26, 2011, at 7:52 PM, Eric Wolff wrote:

> Hi,
>
> I hope this isn't a really simple question, I've been struggling  
> with it
> for a while.
>
> I'm looking for a way to get a function to go through a data frame  
> line by
> line, compare fields, and produce a result, kind of a transform and  
> an if
> statement combined (I tried to put them together and it didn't work).
>
> So, consider data Sales:
>
> House number     Inspected    Sold
> 1                           9/2/2011     10/10/2011
> 2                          9/4/2011      10/20/2011
> 3                          10/31/2011    8/28/2011
> 4                           8/3/2011     11/1/2011
>
> I want to find all the records which were inspected after they were  
> sold.
> Ideally, this code would create a fourth field that would be a  
> logical.
>
> I tried
>
> Sales<-transform(Sales, Checked=if(Sales$Inspected <= Sales$Sold)  
> "OK")

dat <- within(x, Checked <-  as.Date(Inspected, format="%m/%d/%Y") <  
as.Date(Sold, format="%m/%d/%Y"))

Note: it might have been easier if you had converted those string or  
factor variables into R Date variables.

--

David Winsemius, MD
West Hartford, CT