[R] Searching for the first two characters of a string

[David Winsemius]

On Nov 21, 2011, at 10:00 AM, aclinard wrote:

> Remko,
>
> Thank you for your reply. When I try your code, I'm getting the  
> following
> error:
>
> acts10 <-read.table('RailAccident10.txt',sep=',',header=T)
>> acts11 <- acts10[acts10$ACCDMG > 10^5,]
>> h.test <- substr(acts11$CAUSE,1,1)
>> h.data <- acts11[h.test == 'H']

MIssing comma about here ........^

> Error in `[.data.frame`(acts11, h.test == "H") :
>  undefined columns selected

The error message is telling you that you tried to select a colum nad  
you should have thought to yourself:
" a "column"?
    I wanted a row.
    So what have I done that made the "[" function "think" I wanted a  
column?

(Yes, I know that computers can't think. But they can report what they  
were attempting to do when they "gave up" in desperation about being  
told to do impossible things by their owners. )
>
> To confirm that acts11$CAUSE is there, I did this:
> summary(substr(acts11$CAUSE,1,1)=='H')
>
> And got this:
>
>   Mode   FALSE    TRUE    NA's
> logical     393     156       0
>
> Any idea what I'm doing wrong?
>
> Thanks again, I really appreciate your help.
> On Sun, Nov 20, 2011 at 7:13 PM, Remko Duursma [via R] <
> ml-node+s789695n4090042h18 at n4.nabble.com> wrote:
>
>>
>> dfr <- data.frame(txt= c("abab","ghghg","ththt","dfdfdf"), yvar=1:4)
>>
>> ind <- substr(dfr$txt,1,2)
>>
>> dfr[ind == "ab",]
>>
>>
>>
>> greetings,
>> Remko
>>
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David Winsemius, MD
West Hartford, CT