How can I access row labels within gretl?

Question

I have a number of data files which I would like to process with a gretl script. Each file contains a set of annual figures,
e.g.

year, total
1956, 1639
1957, 790
1958, 1150
1959, 909
1960, 1241

When the above sample data is loaded gretl reports:

parsing sample.txt...  
using delimiter ','  
   longest line: 12 characters  
   first field: 'year'  
   seems to be observation label  
   number of columns = 2  
   number of variables: 1  
   number of non-blank lines: 6  
scanning for variable names...  
   line: year,total  
scanning for row labels and data...  
   first row label "1956", last label "1960"  
trying to parse row labels as dates...  
   1956: probably a year... and just a year  
taking date information from row labels    

How can I access the 'first row label' and 'last label' within a script?

Answer 1

given your data set, gretl already recognizes it as a time-series data set with 5 period observations. Printing the initial and last observation label is quite simple.

The obslabel() function converts the observation number into a date string (depending on the underlying observation frequency).

Furthermore, $t1 and $t2 are accessors, returning the observation period (integer value) of the initial observation and the last observation, respectively, of the currently selected sample. The accessor $tmax returns the observation number of the last observation of the overall data set.

Accessing the 'first row label' and 'last label' can be done by:

string first_obs =  obslabel($t1)
string last_obs =  obslabel($t2)
string last_obs_2 = obslabel($tmax)
print first_obs last_obs last_obs_2

Returns:

1956
1960
1960