obtaining a true/false vector with combination of strsplit, length, unlist,

Hi, 

A pared down version of the dataset I'm working with:

edm<-read.table(textConnection("WELLID        X_GRID Y_GRID LAYER ROW COLUMN
SPECIES CALCULATED     OBSERVED
w301_3          4428.       1389     2   6     18       1       3558   
6490.
w304_12         4836.       6627     2  27     20       1       3509   
3228.
02_10_12080    3.6125E+04  13875     1  56    145       1       2774  
-999.0
02_10_12080    3.6125E+04  13875     1  56    145       1       2774  
-999.0
02_10_12081    3.6375E+04  13875     1  56    146       1       3493  
-999.0
02_10_12092    3.9125E+04  13875     1  56    157       1       4736  
-999.0
w305_12         2962.       7326     2  30     12       1       4575   
5899."),header=T)
closeAllConnections() 

I'm having a hard time coming up with the R code that would produce a
TRUE/FALSE vector based on whether or not the first column of the data.frame
"edm" has a length of 2 or 3?  To show what I mean going row-by-row, I could
do the following:

length(strsplit(as.character(edm$WELLID),"_")[[1]])==3

[1] FALSE

length(strsplit(as.character(edm$WELLID),"_")[[2]])==3

[1] FALSE

length(strsplit(as.character(edm$WELLID),"_")[[3]])==3

[1] TRUE

length(strsplit(as.character(edm$WELLID),"_")[[4]])==3

[1] TRUE

length(strsplit(as.character(edm$WELLID),"_")[[5]])==3

[1] TRUE

length(strsplit(as.character(edm$WELLID),"_")[[6]])==3

[1] TRUE

length(strsplit(as.character(edm$WELLID),"_")[[7]])==3

[1] FALSE

I've fumbled around trying to come up with a line of R code that would
create a vector that looks like:  "FALSE FALSE TRUE TRUE TRUE TRUE FALSE"

The final goal is to use this vector to create two new data.frames, where,
for example, the first contains all the rows of edm in which the first
column has a length of 2 when split using a "_" character.  The second
data.frame would contain all the rows in which the first column has a length
of 3 when split using a "_" character.

Thanks,
Eric

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