回复 第1楼 的 chouyu:
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citydata = data.frame(cityname = sample(x = LETTERS,size = 100*26,replace = TRUE),x = rnorm(100*26))<br />
aggregate(citydata[,2],by = list(cityname = citydata[,1]),quantile,probs=0.3)<br />
tapply(citydata[,2],INDEX =citydata[,1],FUN = quantile,probs=0.3)<br />
library(plyr)<br />
ddply(citydata,.(cityname),summarise,quantile = quantile(x,probs = 0.3))<br />
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