With a dataframe data structure and some adjusts and some functions modifications it could be doing like:
data1 . # perhaps the space after . is intentional to bring the idea of pipes replace f(x) with x . f() <https://github.com/tidyverse/magrittr> left_join(data2, by={ x = columname_on_data1, y = columname_on_data2} by calling the column on the join will be performed as a variable. I found a module that implements the dataframe data structure in Perl5 but I didn't find it to Raku. But, I'm thinking in learn Raku better by implementing a DataFrame data structure (as R and Pandas-Python) and some relational function or grammar (as R tidyverse/dplyr <https://github.com/tidyverse/dplyr>) to manipulate data. What are the variations of this grep to left, right, and outer joins? On Sun, Jul 19, 2020 at 5:42 PM Darren Duncan <dar...@darrenduncan.net> wrote: > This reminds me of my 2009 Set::Relation Perl module, which works to help > you do > SQL features like this in your application, but will soon be superseded by > another module that also has a Raku version. -- Darren Duncan > > On 2020-07-19 1:02 p.m., Joseph Brenner wrote: > > I was thinking about the cross-product operator the other day, > > and I was wondering if there might be a convenient way of > > filtering the resulting cartesian product to do something like a > > database inner join: > > > > my @level = ( godzilla => 9 , gremlin => 3, hanuman => 5 ); > > my @origin = ( godzilla => 'jp', tingler => 'us', hanuman => 'il' > ); > > > > my @results = ( @level X @origin ).grep({ $_[0].keys eq $_[1].keys > }); > > say @results; # ((godzilla => 6 godzilla => jp) (hanuman => 5 > > hanuman => il)) > > > > That's easy enough, though the resulting data structure isn't very neat. > > I started looking for ways to rearrange it: > > > > my %joined; > > for @results -> $row { > > say "row: ", $row; # e.g. row: (godzilla => 9 godzilla > => jp) > > say $row.map({ .keys }); # e.g. ((godzilla) (godzilla)) > > say $row.map({ .values }); # e.g. ((9) (jp)) > > > > my $monster =| $row[0].keys; # e.g. godzilla > > my @attributes =| $row.map({ .values }); # e.g. [9 jp] > > %joined{ $monster } = @attributes; > > } > > say %joined; # {godzilla => [9 jp], hanuman => [5 il]} > > > > I can do it more compactly, but it risks getting unreadable: > > > > my %joined2 =| @results.map({ $_[0].keys => .map({ .values }).flat > }); > > > > In any case, the %joined structure feels more perlish, for > > example it's easier to use it to generate reports: > > > > for %joined.keys -> $key { > > printf "%12s: level: %-2d origin: %3s\n", $key, %joined{ $key > }.flat; > > } > > # hanuman: level: 5 origin: il > > # godzilla: level: 9 origin: jp > > > > Is there some neater way of doing this that I'm missing? > > > -- Aureliano Guedes skype: aureliano.guedes contato: (11) 94292-6110 whatsapp +5511942926110
