search for: underdanding

I am having a series of problems using date time data that has been converted into a POSIXt and POSIXlt classes. I have hourly time series data from 1900 that has been converted from text data. I assume most of my problems come from a mis-underdanding of the POSIX class. My matrix named (aa) for this year is approx 8700 by 4. When I try to calculate the length of posit column ( which is the date and time) I get > length(aa$posit) [1] 9 When I try to combined POSIX columns or manipulate them like matrices, I have problems such as &gt...