n.record <- length(record.lenths$NR)
index <- record.lenths$NR %in% valida.records$NR
tmp <- 1:n.record
ind <- tmp[index]
st <- 1
skip <- rep(0,length(ind))
for(i in 1:length(ind)){
if(st<ind[i]){
skip[i]<-sum(record.lenths$
length[st:(ind[i]-1)])
}
st <- ind[i]+1
}
2013/9/12 Zhang Weiwu <zhangwe...@realss.com>
>
> I've got two data frames, as shown below:
> (NR means Number of Record)
>
> record.lenths
>>
> NR length
> 1 100
> 2 130
> 3 150
> 4 148
> 5 100
> 6 83
> 7 60
>
> valida.records
>>
> NR factor
> 1 3
> 2 4
> 4 8
> 7 9
>
> And I intend to obtain the following skip-table:
>
> skip.table
>>
> NR skip factor
> 1 0 3
> 2 0 4
> 4 150 8
> 7 183 9
>
>
> The column 'skip' is the space needed to skip invalid records.
>
> For example, the 3rd element of skip.table has skip of '150', intended to
> skip the invalid record No.3 in record.lengths
>
> For example, the 4th element of skip.table has skip of '183', intended to
> skip the invalid record No.5 and No.6, together is 100+83.
>
> It's rather apparently intended for reading huge data files, and looks
> simple math, and I admit I couldn't find an R-ish way doing it.
>
> Thanks in advance and also thanks for pointing out if I had been on the
> right track to start with.
>
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>
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