r - Using dplyr group_by summarise how to keep a variable occuring at the maximum of another variable? -

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for example, using airquality data, want calculate maximum temperature each month. keep day on maximum temperature occurred.

library(dplyr) # maximum temperature per month airqualitymax <- airquality %>%      group_by(month) %>%      summarise(maxtemp = max(temp)) # day of month on max occured airquality %>%      left_join(airqualitymax, = "month") %>%     filter(temp == maxtemp)

now appears day not unique, suppose unique, there way select day on maximum occurs in summarise() directly?

we can use slice keep row have maximum 'temp' each 'month'

airquality %>%     group_by(month) %>%     slice(which.max(temp))

a faster option arrange 'temp' in descending (or ascending) , first observation (or last slice(n()))

airquality %>%   group_by(month) %>%   arrange(desc(temp)) %>%   slice(1l)

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