[ferret_users] defining time axis

[Arijeet Dutta <arijeet.uoh@xxxxxxxxx>]

Hi all
I have monthly current data (observation) from 2001 to 2011, with many
of the months of 2009 having no observation and hence no data. I
wanted to produce a plot where I can get only the April months from
2001 to 2011 in the time axis. So I found posts helpful from ferret
archive and I did the following

yes? yes?      let L_indx    = L[GT=u_adcp]
yes? yes?      let yr_months = L_indx- 12*INT((L_indx-1)/12)
yes? yes?      let mask_other_months = IF yr_months GT 3 AND yr_months
LT 5 THEN 1
yes? yes?      let u_adcp_masked = u_adcp * mask_other_months
yes? yes?      let u_adcp_compr  = COMPRESSL(u_adcp_masked)

Now u_adcp_compr gives 10 data points since 2009 data for april is
missing. But I want a plot where 2009 april data should show missing
value but when I am doing

yes? yes?      define axis/t=1:11:1 t11
yes? yes?      let u_adcp_april_all = u_adcp_compr[gt=t11@ASN]

u_adcp_april_all shows 11th data points with the missing one being the
11th one but I want 9th one to be missing; how can I better define the
time axis to avoid the problem??
Thanks
Arijeet