Dear Help-Rs,
 
I have data similar to the following:
 
DF <- structure(list(X = 1:22, RESULT = structure(c(2L, 2L, 2L, 2L, 
2L, 2L, 2L, 2L, 2L, 2L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 
1L, 1L), .Label = c("NEG", "POS"), class = "factor"), YR_MO = c(201011L, 
201012L, 201101L, 201102L, 201103L, 201104L, 201105L, 201106L, 
201107L, 201108L, 201109L, 201011L, 201012L, 201101L, 201102L, 
201103L, 201104L, 201105L, 201106L, 201107L, 201108L, 201109L
), TOT_TESTS = c(66L, 98L, 109L, 122L, 113L, 111L, 113L, 146L, 
124L, 130L, 120L, 349L, 393L, 376L, 371L, 396L, 367L, 406L, 383L, 
394L, 412L, 379L)), .Names = c("X", "RESULT", "YR_MO", "TOT_TESTS"
), class = "data.frame", row.names = c(NA, -22L))
 
Currently there are 2 observations for each month (one for negative and one for positive test results).  What I need to create a data set that looks like the following, with positive and negative test results in the same row organized by month:
 
DF2<-structure(list(X = 1:11, RESULT = structure(c(1L, 1L, 1L, 1L, 
1L, 1L, 1L, 1L, 1L, 1L, 1L), .Label = "POS", class = "factor"), 
    YR_MO = c(201011L, 201012L, 201101L, 201102L, 201103L, 201104L, 
    201105L, 201106L, 201107L, 201108L, 201109L), POS_TESTS = c(66L, 
    98L, 109L, 122L, 113L, 111L, 113L, 146L, 124L, 130L, 120L
    ), NEG_TESTS = c(349L, 393L, 376L, 371L, 396L, 367L, 406L, 
    383L, 394L, 412L, 379L)), .Names = c("X", "RESULT", "YR_MO", 
"POS_TESTS", "NEG_TESTS"), class = "data.frame", row.names = c(NA, 
-11L))
 
As this is something that I understand Hadley Wickham's Reshape package is ideally suited for, I tried using the following reshape command:
 
ReshapeDF <- recast(DF, YR_MO~variable)
 
I get the following error message:
 
Using RESULT as id variables
Error: Casting formula contains variables not found in molten data: YR_MO
 
I have a work around that allows me to get to my desired endpoint that involves splitting the data.frame into two (by test result), then using the YR_MO as the by.x/by.y in a merge, but I think this task would be handled more efficiently using reshape?  Can anyone help me to see where I'm going wrong?  Thanks in advance!

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