question

From: Svetlana Eden

Hi everybody.

The question:
I get two vectors 'iFalseFalse' and 'i2'.
I think they should be the same but they are not.
Is it because 
R does not handle complicated logical expressions in such cases 
or I do something wrong?

z1 = c(NA, "", 3, NA, "", 3)
z2 = c("", "", 3, NA, 3, NA)
cV = (as.character(z1)==as.character(z2))
cV

[1]    NA  TRUE  TRUE    NA FALSE    NA

iFalse = (c(1:(length(z1))))[(cV==FALSE)]
iNonNA = (c(1:(length(z1))))[(!(is.na(cV)))]
iFalse

[1] NA NA  5 NA

iNonNA

[1] 2 3 5

iFalseFalse = intersect(iFalse, iNonNA)
iFalseFalse

[1] 5

i2 = (c(1:(length(z1))))[( (cV==FALSE)&&(!(is.na(cV))) )]
i2

numeric(0)

-- 
Svetlana Eden        Biostatistician II            School of Medicine
                     Department of Biostatistics   Vanderbilt 
University