R help - Aug 2009 - Infix all.equal operator for vectors of unequal length

I was trying to use all.equal inside subset() and getting errors  
because I was comparing vectors of unequal length (a column versus a  
constant). I defined an function that did not throw the same errors,  
but wondered if something similar (and probably better designed than  
my noobish attempt) had already been described. Searching on all.equal  
and infix did not produce any results with RSiteSearch.


set.seed(23)
  df1 <- data.frame(a= rnorm(10), b=letters[1:10])
  df1
  subset(df1, all.equal(a, 0.19321233, tol=0.0001))
#Error in subset.data.frame(df1, all.equal(a, 0.19321233, tol =  
1e-04)) :
  # 'subset' must evaluate to logical
all.equal(df1$a, 0.19321233, tol=0.0001)
# [1] "Numeric: lengths (10, 1) differ"

#----
`%=%` <- function(x,y) {abs(x - y) <= .Machine$double.eps ^ 0.5}
#----

  df1$a %=% 0.19321233
# [1]  TRUE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE

subset(df1, a %=% 0.19321233)
#          a b
# 0.1932123 a

(Was a bit surprised that the condition was satisfied with such a low  
tolerance, but was happy with the function working as expected.)

-- 
David Winsemius, MD
Heritage Laboratories
West Hartford, CT