[R] Exclude data using logical

David Winsemius dwinsemius at comcast.net
Thu Mar 25 02:01:52 CET 2010

On Mar 24, 2010, at 7:46 PM, pgseye wrote:

> Hi,
> I'm wanting to exclude data more than 2 sd's from the mean before  
> proceeding
> with further analyses. I've created new logical variables (a and b)  
> and
> written them to the existing dataframe. I want to be able to subset  
> the TRUE
> observations based on another 2 factor variable. I'm assuming this is
> possible, but I don't know what I'm doing wrong, as I get results that
> obviously aren't correct.
> Many thanks,
> Paul
> twin.wide$a<-twin.wide$RCCT<600 & twin.wide$RCCT>480
> twin.wide$b<-twin.wide$LCCT<600 & twin.wide$LCCT>480

> selVarsCCT <- with(twin.wide,c('a','b')) # not sure what that would  
> do. That 'a', 'b' vector would not be interpreted.

I do not think you want to select those columns since they do not have  
the original data, but rather the markers you just created.
> MZCCT <- subset(twin.wide,Zygosity=='MZ',selVarsCCT)
> DZCCT <- subset(twin.wide,Zygosity=='DZ',selVarsCCT)

Assuming you want elements of twin.wide that meet both the conditions  
that a and b are within the range yu slected then try:

MZCCT <- subset(twin.wide, Zygosity=='MZ'& a & b)
# will select all column vales in the qualifying rows.
# add a select= parameter if you only want certain rows

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