> data <- c("2016-03-15 13","2016-03-16 23","2016-03-17 06","2016-03-18 15","2016-03-19 08","2016-03-20 21")
> datevec <- strptime(data,"%Y-%m-%d %H")
> difftime(datevec[-length(datevec)],datevec[-1],units="hours")

##</code><code>##

$R->set( 'data', "2016-03-15 13","2016-03-16 23","2016-03-17 06","2016-03-18 15","2016-03-19 08","2016-03-20 21" );
$R->run( q`datevec <- strptime(data,"%Y-%m-%d %H")` );
$R->run( q`xx <- difftime(datevec[-length(datevec)],datevec[-1],units="hours")` );
@Rres = $R->get('xx');
print Dumper(\@Rres);

##</code><code>##

$VAR1 = [
          [
            'Time',
            'difference',
            'of',
            'hours'
          ]
        ];