32 lines
882 B
R
32 lines
882 B
R
# iterator for splitting data using a factor
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library(foreach)
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# let's use isplit on a data frame
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a <- foreach(i=isplit(airquality, airquality$Month), .combine=rbind) %do%
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quantile(i$value, na.rm=TRUE)
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# make it pretty and print it
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rownames(a) <- levels(as.factor(airquality$Month))
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print(a)
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# use a list of factors to do an aggregated operation
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it <- isplit(as.data.frame(state.x77),
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list(Region=state.region, Cold=state.x77[,'Frost'] > 130),
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drop=TRUE)
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a <- foreach(i=it, .combine=rbind) %do% {
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x <- mean(i$value)
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dim(x) <- c(1, length(x))
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colnames(x) <- names(i$value)
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cbind(i$key, as.data.frame(x))
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}
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print(a)
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# compare with the standard aggregate function
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b <- aggregate(state.x77,
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list(Region=state.region, Cold=state.x77[,'Frost'] > 130),
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mean)
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print(b)
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cat('results identical:\n')
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print(identical(a, b))
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