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2009 Nov 02
1
Avoiding for loops
...I want to normalize PER GROUP as opposed to over the entire data set. The current double loop that I'm using takes almost an hour to run on about 30,000 rows of data in 2,500 groups. I'm currently doing this: ------------------------------------- for(group in unique(data$group)){ sum_V1 <- sum(data$V1[data$group == group]) for(subject in data$subject[data$group == group]){ data$V1_norm[(data$group == group & data$subject == subject)] <- data$V1[(data$group == group & data$subject == subject)] / sum_V1 } } ------------------------------------- Ca...