R help - Dec 2011 - comparing fields within a record

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")

But that busted. I've bent over backward to make these kinds of comparisons
work, but there has to be a better way. Any help would be most welcome.

Thanks,

Eric

	[[alternative HTML version deleted]]

Hi Eric,

Try

# data
x <- structure(list(House_number = 1:4, Inspected = structure(c(3L,
4L, 1L, 2L), .Label = c("10/31/2011", "8/3/2011",
"9/2/2011",
"9/4/2011"), class = "factor"), Sold = structure(c(1L, 2L,
4L,
3L), .Label = c("10/10/2011", "10/20/2011",
"11/1/2011", "8/28/2011"
), class = "factor")), .Names = c("House_number",
"Inspected",
"Sold"), class = "data.frame", row.names = c(NA, -4L))
> with(x, as.Date(Inspected, "%m/%d/%y") - as.Date(Sold,
"%m/%d/%y") > 0)
[1] FALSE FALSE  TRUE FALSE
> x[with(x, as.Date(Inspected, "%m/%d/%y") - as.Date(Sold,
"%m/%d/%y") >
0), ]
  House_number  Inspected      Sold
3            3 10/31/2011 8/28/2011

See ?as.Date for more information.

HTH,
Jorge.-


On Mon, 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")
>
> But that busted. I've bent over backward to make these kinds of
comparisons
> work, but there has to be a better way. Any help would be most welcome.
>
> Thanks,
>
> Eric
>
>        [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help@r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
	[[alternative HTML version deleted]]

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