How to sum by group for all numeric vectors expect character vectors in data.table?

Asked Nov 21 '17 at 10:54

Active Nov 21 '17 at 10:56

Viewed 26 times

I have a data frame which consists of numeric and character vectors for which i am trying to sum all vectors and divide it by 4, my code is as below

df2 =  df1%>%
  group_by(city,name,day,hour, age ,sex) %>%
  summarise_if(is.numeric, function(x) sum(x/4,na.rm =T))

how can we write a same code in data.table package , so that we can save the time. Thanks in advance.

edited Nov 21 '17 at 10:56

David Arenburg

asked Nov 21 '17 at 10:54

sasir

Thanks Henrik, how can we add sum/4 in mydt[, lapply(.SD, sum), .SDcols = cols] – sasir Nov 21 '17 at 11:11
You can pass an "anonymous function" to `lapply`, as described e.g. here: [data.table in R - apply multiple functions to multiple columns](https://stackoverflow.com/questions/29620783/data-table-in-r-apply-multiple-functions-to-multiple-columns) – Henrik Nov 21 '17 at 11:26

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