On 22/07/2009, at 1:21 PM, jim holtman wrote:
Notice that three items are returned where you thought one was:
[1] FALSE TRUE TRUE TRUE FALSE
db1$olditems[db1$olditems==''] #wait, only one item is returned?
[1]
Levels: nuts soup
db1[db1$olditems=='',] #somehow this works!
olditems prices
2 3.25
3 4.42
4 2.25
paste('[',db1$olditems[db1$olditems==''],']') # put some
characters around return values
[1] "[ ]" "[ ]" "[ ]"
The '[1]' was just an indication that this is the first value returned
and the other two were blanks so you did not see them. Also "" is
just that; a blank and not NA.
Strictly speaking --- or maybe even not so strictly --- a ***null
character***,
not a blank. "" != " "
cheers,
Rolf Turner
<snip>
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