[ferret_users] daily average from hourly data

[Dongxiao Zhang <dongxiao.zhang@xxxxxxxx>]

Hi,

I am trying to calculate daily averages from hourly data with data gaps. 
A sample data is attached as test1.cdf.
I tried the following script to get the daily mean. It only works well 
for a timeseries without missing data.

use test1.cdf
def axis/t="31-jul-2010:23:30":"6-aug-2010:00:30":24/unit=hour/edges mytd
set var/bad=1e35 RD_495
let daily=RD_495[gt=mytd@ave]
plot RD_495, daily

The daily mean is defined as the average of 00 to 23 hours of each day. 
We should have missing values for the daily mean if any hour in that 
particular day has missing data. The above script simply averages all 
available data in each day as the mean, which is wrong. Is there a way 
to count how many good data points in each day so that they can be used 
as a mask? Or is there a better way to get daily means?

Thanks for any suggestions!

Dongxiao

Attachment: test1.cdf
Description: Cdf file