CODEWITHSUNDEEP
rdataframe
user5326689
user5326689

Reputation:

Grouping data in R data.frame

What is sql group by equivalent of R For example I want perform this on a data.frame

SELECT MAX(temp) from table group by day

by subset function
Note::

I know about sqldf and I don't want use it for some purpose

Upvotes: 0

Views: 101

Answers (1)

akrun
akrun

Reputation: 887901

We can either use aggregate from base R. Here, I am using the formula method, where the grouping variable is on the RHS of the ~. Specify the FUN as max to get the maximum value of 'temp'

aggregate(temp~day, df1, FUN = max)

Or using dplyr, we group by 'day' and get the max of temp within summarise.

library(dplyr)
df1 %>%
    group_by(day) %>%
    summarise(temp= max(temp))

Or using data.table, we convert the 'data.frame' to 'data.table' (setDT(df1)), grouped by 'day', we get the max of 'temp'.

library(data.table)
setDT(df1)[, list(temp=max(temp)), by = day]

Upvotes: 1

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