Calculating hourly averages from a multi-year timeseries

Question

I have a dataset filled with the average windspeed per hour for multiple years. I would like to create an \'average year\', in which for each hour the average windspeed for

Answer 1

You can use substr to extract the part of the date you want, and then use tapply or ddply to aggregate the data.

tapply(
  data.multipleyears$Windspeed, 
  substr( data.multipleyears$DATETIME, 6, 19), 
  mean 
)
# 01-01 01:00:00 02-29 12:00:00 05-03 09:00:00 
#              9              3              5 

library(plyr)
ddply(
  data.multipleyears, 
  .(when=substr(DATETIME, 6, 19)), 
  summarize, 
  Windspeed=mean(Windspeed)
)
#             when Windspeed
# 1 01-01 01:00:00         9
# 2 02-29 12:00:00         3
# 3 05-03 09:00:00         5