Hi.
I was trying to use "ddply" function for applying my function to dataframe.
When I implemented my code, ddply function didn't working and R session was terminated.
I checked ddply function and I found out "splitter_d" function from plyr caused the problem.

There was a POSIXlt date class field in the dataframe. But the variable was not used in calculation.
I think "Splitter_d" function doesn't working well and can't split data into sub pieces if POSIXlt class field is in dataframe.
My function worked for first splitted data but didn't work for 2nd sub data.
But after changing date class to POSIXct, the code worked well.