[R] need technique for speeding up R dataframe individual element insertion (no deletion though)
ishwor.gurung at gmail.com
Thu Aug 13 14:07:17 CEST 2009
I am working on a dataframe cam and it involves comparison within the
2 columns - t1 and t2 on about 20K rows and 14 columns.
cap = cam; # this doesn't take long. ~1 secs.
for( i in 1:length(cam$end_date))
if(!is.na(x2) && !is.na(x1) && !is.na(t1) && !is.na(t2))
if( (x2>=x1) && (t1==t2) ) # date and vol
cap$levels[i]=1; #make change to specific dataframe cell
Having coded that, i ran a timing profile on this section and each
1000'th row comparison is taking ~1.1 minutes on a 2.8Ghz dual-core
box (which is a test box we use).
This obviously computes to ~21 minutes for 20k which is definitely not
where we want it headed. I believe, optimisation(or even different way
to address indexing inside dataframe) can be had inside the innermost
`if' and specifically in `cap$levels[i]=1;' but I am a bit at a loss
having scoured the documentation failing to find anything of value.
So, my question remains are there any general/specific changes I can
do to speed up the code execution dramatically?
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