Group rows in data frame based on time difference between consecutive rows

Question

I have a data frame of this type

YEAR   MONTH  DAY  HOUR       LON      LAT

1860     10      3   13      -19.50   3.00          
1860     10      3   17             


        

Answer 1

I would try something along these lines. Since you mention that you only need to figure out the subsetting logic, I haven't bothered to add the correlation coeff calculation.

df$date <- as.Date(paste(df$YEAR,df$MONTH,df$DAY),'%Y %m %d')

uniquedates <- unique(df$date)
uniquedatesfourth <- uniquedates + 4

for ( i in seq(length(uniquedates)))
{
   tempsubset <- subset(df, date >= uniquedates[i] & date >= uniquedatesfourth[i])
   # operations on tempsubset
}