On Feb 25, 2005, at 6:06 AM, Firas Swidan wrote:
Hi,
I am experiencing a long delay when using dataframes inside loops and was
wordering if this is a bug or not.
Example code:
st <- rep(1,100000) ed <- rep(2,100000) for(i in 1:length(st)) st[i] <- ed[i] # works fine df <- data.frame(start=st,end=ed) for(i in 1:dim(df)[1]) df[i,1] <- df[i,2] #takes for ever
R: R 2.0.0 (2004-10-04) OS: Linux, Fedora Core 2 kernel: 2.6.10-1.14_FC2 cpu: AMD Athlon XP 1600. mem: 500MB.
The example above is only to illustrate the problem. I need loops to apply
some functions on pairs (not necessarily successive) of rows in a
dataframe.
I'm not an expert, but working with dataframes is typically slower than the eqivalent matrix. If it is possible (the data is of the same type, as it is above), working with the equivalent matrix is prabably faster. So, I think the general answer to the implied question is that dataframe processing is slower than vector processing or the equivalent matrix processing.
If you post more details about your specific problem, folks may be able to find creative ways of speeding things up, if speed remains a concern.
Sean
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