Return maximum values for a set of combinations

[Odiri Metieh]

I want to return the highest number from a column for a specific country in a specific month and a specific year. I have 255 countries, 12 months and 3years. The code below was what I used but it kept giving me this error - "variable max_cases already defined". I checked over many times and I can't seem to find the solution. Can anyone help please? Thank you.

gen maxcases = .

// Get the unique values of the country variable
levelsof iso_code, local(country_list)

// Loop through different combinations of countries, months, and years
foreach country in `country_list' {
foreach month in 1/12 {
foreach year in 1 2 3 {
// Calculate the maximum number of cases for the current combination
egen max_cases = max(cases) if iso_code == "`country'" & month_id == `month' & year_id == `year'

// Update the maxcases variable with the maximum number of cases
replace max_cases = maxcases if iso_code == "`country'" & month_id == `month' & year_id == `year'
}
}
}

[Clyde Schechter]

You create the variable max_cases the first time through the loop. When you come back the second time, it already exists, so you cannot -egen- it again.

But there is no reason to do this with any loops.

by iso_code month_id year_id, sort: egen max_cases = max(cases)

is all you need.