I am using a "for" loop to read a table row by row and I have to specify how
many records are there in the table. I need to read row by row because the
table is huge and the memory not large enough for the whole table.:
number.of.records=100
fp=file("abc.csv","r")
pos=seek(fp, rw="read")
for (i in 1:number.of.record){
current.row=scan(file=fp, sep=',', what=list(count=1, cusip6="", idate=1,
spread=1.1, vol252=1.1, vol1000=1.1, st_debt=1.1, lt_debt=1.1 , total_liab=
1.1, cr=1.1, shrout=1.1, prc=1.1, mkt_cap=1.1, rtng=1.1, sec=1.1, cr3m=1.1,
cr5y=1.1, ust3m=1.1, ust5y=1.1), flush=TRUE, nlines=1,quiet=T)
...
}
I need to know the number of records in the table and put it in the variable
named "number.of.records". When I have a new table that I do not know how
many records it has, I use excel to open the file to figure it out and put
it in variable " number.of.records". I often have many tables to try and
every one of them has thousands of records----it takes a lot of time and
trouble to adjust the code every time I read a different table.
I am wondering if I can change the "for" loop to a "while" loop:
while (the end of the table has not been reached)
{
current.row=scan(file=fp, sep=',', what=list(count=1, cusip6="", idate=1,
spread=1.1, vol252=1.1, vol1000=1.1, st_debt=1.1, lt_debt=1.1 , total_liab=
1.1, cr=1.1, shrout=1.1, prc=1.1, mkt_cap=1.1, rtng=1.1, sec=1.1, cr3m=1.1,
cr5y=1.1, ust3m=1.1, ust5y=1.1), flush=TRUE, nlines=1,quiet=T)
...
}
The problem is how to articulate "while (the end of the table has not been
reached)", or equivalently, how to signal the end of the table?
Best Wishes
Yuchen Luo
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