Converting annual data to semiannual

[Luca Manzoni]

Hi everyone, i have to convert a set of annual observations about debt and deficit gdp ratios into semiannual, can someone hepl me? It's important. I leave here an extract of my dataset (data only for belgium)

location year debt_gdp pd_gdp
BEL 1996 129 -4.002527
BEL 1997 124.3 -2.151257
BEL 1998 119.2 -1.024874
BEL 1999 115.4 -.6483495
BEL 2000 109.6 -.0792975
BEL 2001 108.2 .2328486
BEL 2002 105.4 -.0436953
BEL 2003 101.7 -1.864152
BEL 2004 97.2 -.2386971
BEL 2005 95.1 -2.714993
BEL 2006 91.5 .2395806
BEL 2007 87.3 .0664399
BEL 2008 93.2 -1.095345
BEL 2009 100.2 -5.430989
BEL 2010 100.3 -4.087706
BEL 2011 103.5 -4.330078
BEL 2012 104.8 -4.318382
BEL 2013 105.5 -3.129378
BEL 2014 107 -3.055682
BEL 2015 105.2 -2.413671
BEL 2016 105 -2.363113
BEL 2017 102 -.6864632
BEL 2018 99.8 -.7937546

Thank you in advance

[Nick Cox]

And how do you propose to do that? There is no information here that would give different values for the first and second halves of any year.

[Luca Manzoni]

And with these type of dataset?
location time_cal debt_gdp pd_gdp
BEL 1996 129 -4.002527
BEL 1996.5
BEL 1997 124.3 -2.151257
BEL 1997.5
BEL 1998 119.2 -1.024874
BEL 1998.5
BEL 1999 115.4 -.6483495
BEL 1999.5
BEL 2000 109.6 -.0792975
BEL 2000.5
BEL 2001 108.2 .2328486
BEL 2001.5
BEL 2002 105.4 -.0436953
BEL 2002.5
BEL 2003 101.7 -1.864152
BEL 2003.5
BEL 2004 97.2 -.2386971
BEL 2004.5
BEL 2005 95.1 -2.714993
BEL 2005.5
BEL 2006 91.5 .2395806
BEL 2006.5
BEL 2007 87.3 .0664399
BEL 2007.5
BEL 2008 93.2 -1.095345
BEL 2008.5
BEL 2009 100.2 -5.430989
BEL 2009.5
BEL 2010 100.3 -4.087706
BEL 2010.5
BEL 2011 103.5 -4.330078
BEL 2011.5
BEL 2012 104.8 -4.318382
BEL 2012.5
BEL 2013 105.5 -3.129378
BEL 2013.5
BEL 2014 107 -3.055682
BEL 2014.5
BEL 2015 105.2 -2.413671
BEL 2015.5
BEL 2016 105 -2.363113
BEL 2016.5
BEL 2017 102 -.6864632
BEL 2017.5
BEL 2018 99.8 -.7937546
BEL 2018.5

i've created missing values for each second half of the year.

[Nick Cox]

#2 is not answered. You should use half-yearly dates as explained at

help datetime