[R] Selecting from a character vector with logical operators

[Chuck Cleland]

   With a character vector it works fine, but your ca11c93SOL1$RECTAN 
seems to be a factor.

 > letters[letters > "j"]
  [1] "k" "l" "m" "n" "o" "p" "q" "r" "s" "t" "u" "v" "w" "x" "y" "z"

 > letfact <- as.factor(letters)
 > letfact[letfact > "j"]
  [1] <NA> <NA> <NA> <NA> <NA> <NA> <NA> <NA> <NA> <NA> <NA> <NA> <NA> 
<NA> <NA>
[16] <NA> <NA> <NA> <NA> <NA> <NA> <NA> <NA> <NA> <NA> <NA>
Levels: a b c d e f g h i j k l m n o p q r s t u v w x y z
Warning message:
">" not meaningful for factors in: Ops.factor(letfact, "j")

Robert Brown FM CEFAS wrote:
> I'm trying to select a subset from character vector using the logical operator >, but get the following error 
> 
> 6356     85     SOL   1     25     1   38E6
> 6357     85     SOL   1     27     1   38E6
> 6910     95     SOL   1     25     1   38E6
> 7152     98     SOL   1     19     1   38E6
> 7153     98     SOL   1     22     2   38E6
> 7154     98     SOL   1     28     1   38E6
> 
>>ca11c93SOL1VIIa<-ca11c93SOL1[ca11c93SOL1$RECTAN>"32Z9",]
> 
> Warning message: 
> ">" not meaningful for factors in: Ops.factor(ca11c93SOL1$RECTAN, "32Z9") 
> 
> (note RECTAN is the name assigned to the 7 th column)
> 
> Do these operators act on chacters vectors as opposed to numeric vectors and if so what are the rules for this?
> 
> Regards,
> 
> Robert Brown
> 
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-- 
Chuck Cleland, Ph.D.
NDRI, Inc.
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