如何选择dplyr组中具有最大值的行?
set.seed(1)df <- expand.grid(list(A = 1:5, B = 1:5, C = 1:5))df$value <- runif(nrow(df))
library(plyr)ddply(df, .(A, B), function(x) x[which.max(x$value),])
library(dplyr)df %>% group_by(A, B) %>% summarise(max = max(value))
sessionInfo()R version 3.1.0 (2014-04-10)Platform: x86_64-w64-mingw32/x64 (64-bit)locale:[1] LC_COLLATE=English_Australia.1252 LC_CTYPE=English_Australia.1252 [3] LC_MONETARY=English_Australia.1252 LC_NUMERIC=C [5] LC_TIME=English_Australia.1252 attached base packages:[1] stats graphics grDevices utils datasets methods base other attached packages:[1] dplyr_0.2 plyr_1.8.1 loaded via a namespace (and not attached):[1] assertthat_0.1.0.99 parallel_3.1.0 Rcpp_0.11.1 [4] tools_3.1.0
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