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#1: Merging/Joining AoA

Posted on 2008-04-22 08:35:53 by Vishal G

Hi Guys,

I have a little complicated problem...

I have two arrays

@a = ( ['id', 'name', 'age'],
['1', 'Fred', '24'],
['2', 'Frank', '42'],
);

@b = ( ['id', 'sex'],
['1', 'm' ],
['2', 'm'],
);

I want to join these two AoA, based on id, so the resulting array will
look like this

@c = ( ['id', 'name', 'age', 'sex'],
['1', 'Fred', '24', 'm' ],
['2', 'Frank', '42', 'm'],
);

Any Ideas?

Thanks in advance.

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#2: Re: Merging/Joining AoA

Posted on 2008-04-22 09:13:35 by benkasminbullock

On Apr 22, 3:35 pm, Vishal G <v3gu...@gmail.com> wrote:
> Hi Guys,
>
> I have a little complicated problem...
>
> I have two arrays
>
> @a = ( ['id', 'name', 'age'],
> ['1', 'Fred', '24'],
> ['2', 'Frank', '42'],
> );
>
> @b = ( ['id', 'sex'],
> ['1', 'm' ],
> ['2', 'm'],
> );
>
> I want to join these two AoA, based on id, so the resulting array will
> look like this
>
> @c = ( ['id', 'name', 'age', 'sex'],
> ['1', 'Fred', '24', 'm' ],
> ['2', 'Frank', '42', 'm'],
> );
>
> Any Ideas?

my %akeys;
@akeys{map $$_[0],@a} = @a;
my %bkeys;
@bkeys{map $$_[0],@b} = @b;
my @c;
for (sort keys %akeys) {
if ($bkeys{$_}) {
push @c, [@{$akeys{$_}},@{$bkeys{$_}}[1..$#{$bkeys{$_}}]];
}
}
for (@c) {
print "[",join (", ",@$_),"]\n";
}

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#3: Re: Merging/Joining AoA

Posted on 2008-04-22 14:26:31 by Mpapec

Vishal G wrote:
> I have a little complicated problem...
>
> I have two arrays
>
> @a = ( ['id', 'name', 'age'],
> ['1', 'Fred', '24'],
> ['2', 'Frank', '42'],
> );
>
> @b = ( ['id', 'sex'],
> ['1', 'm' ],
> ['2', 'm'],
> );
>
> I want to join these two AoA, based on id, so the resulting array will
> look like this
>
> @c = ( ['id', 'name', 'age', 'sex'],
> ['1', 'Fred', '24', 'm' ],
> ['2', 'Frank', '42', 'm'],
> );

Assuming that both @a and @b have same size and same id order,

for my $i (0 .. $#a) {
my $at = $a[$i];
my $bt = $b[$i];
push @$at, @$bt[1 .. $#$bt];
}
use Data::Dumper;
print Dumper \@a;

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#4: Re: Merging/Joining AoA

Posted on 2008-04-22 16:24:19 by Hartmut Camphausen

In <<7d3db66d-5cef-4eaa-8cd3-54e489ae1721@a5g2000prg.googlegroups.com>>
schrieb Ben Bullock...

> [...]
> my @c;
> for (sort keys %akeys) {
> [...]
> }
> for (@c) {
> print "[",join (", ",@$_),"]\n";
> }

Prints [1, Fred, 24, m]
[2, Frank, 42, m]
[id, name, age, sex]

Take care of the 'sort' ;-)


Alternatively, if you want to take care of the IDs of /both/ arrays,
you could write:


#!perl.exe -w # well, on Windows...
use strict; # always 'use' this one!

my @a = ( ['id', 'name', 'age' ], # just our data...
['2', 'Frank', '42' ],
['1', 'Fred', '24' ],
['3', 'Pat', '36' ],
);
my @b = ( ['id', 'sex' ], # ...to deal with
['1', 'm' ],
['2', 'm' ],
['4', '??' ],
);

my @afields = @{ shift @a }; # get rid of field names,
my @bfields = @{ shift @b }; shift @bfields; # keeping them at hand
my %a = map {$_->[0], $_} @a; # now we can refer to the...
my %b = map {shift @{$_}, $_} @b; # ...data by their IDs

my %seen; # just to avoid duplicates
my @c = ( [ @afields, @bfields ], # field names come first
map { [ $a{$_} ? @{$a{$_}} : ($_, ('') x $#afields),
$b{$_} ? @{$b{$_}} : ( ('') x @bfields )
]
} sort grep { $seen{$_}++ ? 0 : $_ }
keys (%a), keys (%b)
);


....gives

['id', 'name', 'age', 'sex']
['1', 'Fred', '24', 'm' ]
['2', 'Frank', '42', 'm' ]
['3', 'Pat', '36', '' ]
['4', '', '', '??' ]



mfg, Hartmut


--
------------------------------------------------
Hartmut Camphausen h.camp[bei]textix[punkt]de

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#5: Re: Merging/Joining AoA

Posted on 2008-04-22 17:11:23 by it_says_BALLS_on_your forehead

On Apr 22, 2:35=A0am, Vishal G <v3gu...@gmail.com> wrote:
> Hi Guys,
>
> I have a little complicated problem...
>
> I have two arrays
>
> @a =3D ( ['id', 'name', 'age'],
> =A0 =A0 =A0 =A0 =A0 =A0['1', 'Fred', '24'],
> =A0 =A0 =A0 =A0 =A0 =A0['2', 'Frank', '42'],
> =A0 =A0 =A0 =A0 =A0);
>
> @b =3D ( ['id', 'sex'],
> =A0 =A0 =A0 =A0 =A0 =A0['1', 'm' ],
> =A0 =A0 =A0 =A0 =A0 =A0['2', 'm'],
> =A0 =A0 =A0 =A0 =A0);
>
> I want to join these two AoA, based on id, so the resulting array will
> look like this
>
> @c =3D ( ['id', 'name', 'age', 'sex'],
> =A0 =A0 =A0 =A0 =A0 =A0['1', 'Fred', '24', 'm' ],
> =A0 =A0 =A0 =A0 =A0 =A0['2', 'Frank', '42', 'm'],
> =A0 =A0 =A0 =A0 =A0);
>
> Any Ideas?

I'm not sure how much control you have over the structure of the data,
but it seems to me that you would be better served if the data were
stored in hashes to begin with:

use strict; use warnings;
use Data::Dumper;

my %people =3D (
1 =3D> { name =3D> 'Fred', age =3D> 24 },
2 =3D> { name =3D> 'Frank', age =3D> 42 },
);

my %gender =3D (
1 =3D> { sex =3D> 'm' },
2 =3D> { sex =3D> 'm' },
);

=2E..then it's a simple matter to combine the two structures, keyed by
the id.

for my $id ( keys %people ) {
$people{$id}{sex} =3D $gender{$id}{sex};
}



print Dumper( \%people ), "\n";

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#6: Re: Merging/Joining AoA

Posted on 2008-04-22 17:30:37 by benkasminbullock

On Tue, 22 Apr 2008 16:24:19 +0200, Hartmut Camphausen wrote:

> Prints [1, Fred, 24, m]
> [2, Frank, 42, m]
> [id, name, age, sex]

Yes, I know. So what?

> Take care of the 'sort' ;-)

I don't care about the order of these results. The original poster can
figure out all the details if he wants to.

> Alternatively, if you want to take care of the IDs of /both/ arrays, you
> could write:

Yes, but I have no way to really guess in detail what the original poster
wanted, so why spend a lot of time trying to cover every possibility? I
wrote that initial answer in only a minute or two, and I think it's good
enough to get the poster on track towards an answer.

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#7: Re: Merging/Joining AoA

Posted on 2008-04-22 17:51:18 by it_says_BALLS_on_your forehead

On Apr 22, 11:11=A0am, nolo contendere <simon.c...@fmr.com> wrote:
> On Apr 22, 2:35=A0am, Vishal G <v3gu...@gmail.com> wrote:
>
>
>
> > Hi Guys,
>
> > I have a little complicated problem...
>
> > I have two arrays
>
> > @a =3D ( ['id', 'name', 'age'],
> > =A0 =A0 =A0 =A0 =A0 =A0['1', 'Fred', '24'],
> > =A0 =A0 =A0 =A0 =A0 =A0['2', 'Frank', '42'],
> > =A0 =A0 =A0 =A0 =A0);
>
> > @b =3D ( ['id', 'sex'],
> > =A0 =A0 =A0 =A0 =A0 =A0['1', 'm' ],
> > =A0 =A0 =A0 =A0 =A0 =A0['2', 'm'],
> > =A0 =A0 =A0 =A0 =A0);
>
> > I want to join these two AoA, based on id, so the resulting array will
> > look like this
>
> > @c =3D ( ['id', 'name', 'age', 'sex'],
> > =A0 =A0 =A0 =A0 =A0 =A0['1', 'Fred', '24', 'm' ],
> > =A0 =A0 =A0 =A0 =A0 =A0['2', 'Frank', '42', 'm'],
> > =A0 =A0 =A0 =A0 =A0);
>
> > Any Ideas?
>
> I'm not sure how much control you have over the structure of the data,
> but it seems to me that you would be better served if the data were
> stored in hashes to begin with:
>
> use strict; use warnings;
> use Data::Dumper;
>
> my %people =3D (
> =A0 1 =3D> { name =3D> 'Fred', =A0age =3D> 24 },
> =A0 2 =3D> { name =3D> 'Frank', age =3D> 42 },
> );
>
> my %gender =3D (
> =A0 1 =3D> { sex =3D> 'm' },
> =A0 2 =3D> { sex =3D> 'm' },
> );
>
> ...then it's a simple matter to combine the two structures, keyed by
> the id.
>
> for my $id ( keys %people ) {
> =A0 =A0 $people{$id}{sex} =3D $gender{$id}{sex};
>
> }
>
> print Dumper( \%people ), "\n";

One more thing, are you certain that you wanted to quote the age
values in your data? in most cases perl is smart enough to dwym, but
for clarity i think it would be better to leave them as numbers rather
than strings.

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#8: Re: Merging/Joining AoA

Posted on 2008-04-23 05:49:56 by benkasminbullock

nolo contendere <simon.chao@fmr.com> wrote:

> I'm not sure how much control you have over the structure of the data,
> but it seems to me that you would be better served if the data were
> stored in hashes to begin with:

If the person needs to know how to put in a screw, why tell him he
would be better served by using nails and a hammer?

A quote from Stephen King (viewable at
http://www.nsftools.com/blog/blog-03-2006.htm) comes to mind:

"I want to suggest to you that to write to the best of your abilities,
it behooves you to construct your own toolbox and then build up enough
muscle so you can carry it with you. Then, instead of looking at a
hard job and getting discouraged, you will perhaps seize the correct
tool and get immediately to work."

In the real world, there are lots of situations in which you're likely
to get data in an array of arrays. For example if you take data from a
"Range" in an Excel spreadsheet, you'll get it back as an array of
arrays, just like the original poster's problem. Instead of looking at
a hard job and getting discouraged, I'd suggest you think about
seizing the correct tool and getting immediately to work.

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#9: Re: Merging/Joining AoA

Posted on 2008-04-23 06:55:03 by Keith Keller

On 2008-04-23, benkasminbullock@gmail.com <benkasminbullock@gmail.com> wrote:
>
> A quote from Stephen King (viewable at
> http://www.nsftools.com/blog/blog-03-2006.htm) comes to mind:
>
> "I want to suggest to you that to write to the best of your abilities,
> it behooves you to construct your own toolbox and then build up enough
> muscle so you can carry it with you. Then, instead of looking at a
> hard job and getting discouraged, you will perhaps seize the correct
> tool and get immediately to work."

use Shining;

my $shine=Shining->new;
$shine->enterRoom(237);
$shine->avoid('Dad');
$shine->call('cook');
$shine->REDRUM;
$shine->escape('hedgeMaze','snowmobile');

--keith

--keith


--
kkeller-usenet@wombat.san-francisco.ca.us
(try just my userid to email me)
AOLSFAQ=http://www.therockgarden.ca/aolsfaq.txt
see X- headers for PGP signature information

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#10: Re: Merging/Joining AoA

Posted on 2008-04-23 15:22:15 by Ted Zlatanov

On Tue, 22 Apr 2008 21:55:03 -0700 Keith Keller <kkeller-usenet@wombat.san-francisco.ca.us> wrote:

KK> use Shining;

KK> my $shine=Shining->new;
KK> $shine->enterRoom(237);
KK> $shine->avoid('Dad');
KK> $shine->call('cook');
KK> $shine->REDRUM;
KK> $shine->escape('hedgeMaze','snowmobile');

I think you forgot to include the POD:

All work and no play makes Jack a dull boy
All work and no play makes Jack a dull boy
All work and no play makes Jack a dull boy
All work and no play makes Jack a dull boy
All work and no play makes Jack a dull boy
All work and no play makes Jack a dull boy
All work and no play makes Jack a dull boy
All work and no play makes Jack a dull boy
All work and no play makes Jack a dull boy
All work and no play makes Jack a dull boy
All work and no play makes Jack a dull boy
All work and no play makes Jack a dull boy
All work and no play makes Jack a dull boy
All work and no play makes Jack a dull boy
All work and no play makes Jack a dull boy
All work and no play makes Jack a dull boy
All work and no play makes Jack a dull boy
All work and no play makes Jack a dull boy
All work and no play makes Jack a dull boy
All work and no play makes Jack a dull boy
All work and no play makes Jack a dull boy
All work and no play makes Jack a dull boy
All work and no play makes Jack a dull boy
All work and no play makes Jack a dull boy
All work and no play makes Jack a dull boy
All work and no play makes Jack a dull boy
All work and no play makes Jack a dull boy
All work and no play makes Jack a dull boy
All work and no play makes Jack a dull boy
All work and no play makes Jack a dull boy
All work and no play makes Jack a dull boy
All work and no play makes Jack a dull boy

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#11: Re: Merging/Joining AoA

Posted on 2008-04-23 16:46:35 by it_says_BALLS_on_your forehead

On Apr 22, 11:49=A0pm, benkasminbull...@gmail.com wrote:
> nolo contendere <simon.c...@fmr.com> wrote:
> > I'm not sure how much control you have over the structure of the data,
> > but it seems to me that you would be better served if the data were
> > stored in hashes to begin with:
>
> If the person needs to know how to put in a screw, why tell him he
> would be better served by using nails and a hammer?


huh? i began my suggestion with the caveat that this would be relevant
if the OP had the control to choose the data structures in which he
housed his data. to follow up on your analogy, if the person needs to
know how to build a house, and is scratching his head wondering how to
do it with only screws and a screwdriver, yes, i could help him by
telling him how to go about it.

or, i can point out that there is a tool shed around the corner of
which he is unaware, and then proceed to pick out more appropriate
tools that he can use to better build his house.

here's another analogy. if he asked, how do i add the following?
<<END_WORD_PROBLEM;

i want to add three 6's and six 4's using addition. sure, you could
say: well, first compute the sum of the three 6's, like so--
6 + 6 + 6 =3D 18.
then, compute the sum of six 4's, like so--
4 + 4 + 4 + 4 + 4 + 4 =3D 24.
finally, add the two sums together.
18 + 24 =3D 42.
END_WORD_PROBLEM

Or, I could make life a whole lot easier by suggesting:
just do: (3 x 6) + (6 x 4) =3D 42.

what's wrong with that? at the very worst, if there are restrictions
in place that prohibit him from using multiplication for this
particular problem, he is at least aware that there is a better
solution for similar problems in the future, when such restrictions
may may be lifted, or not even exist at all.

=2E..or did you just want an excuse to post that quote by Steven
King? ;-).

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#12: Re: Merging/Joining AoA

Posted on 2008-04-24 00:47:36 by benkasminbullock

On Wed, 23 Apr 2008 07:46:35 -0700, nolo contendere wrote:

> On Apr 22, 11:49 pm, benkasminbull...@gmail.com wrote:

>> If the person needs to know how to put in a screw, why tell him he
>> would be better served by using nails and a hammer?
>
>
> huh? i began my suggestion with the caveat that this would be relevant
> if the OP had the control to choose the data structures in which he
> housed his data. to follow up on your analogy, if the person needs to
> know how to build a house, and is scratching his head wondering how to
> do it with only screws and a screwdriver, yes, i could help him by
> telling him how to go about it.

Well, I'm sorry to offend you.

> ...or did you just want an excuse to post that quote by Steven King?
> ;-).

No, I think it was the correct time to post that quote. Or maybe a more
relevant quote would be something about how if you endlessly try to
finesse things, you'll never actually get the job done. Perl programmers
should know how to deal with awkward data formats like the original
poster's, because these do occur in practice, and they may be unavoidable
for one reason or another.

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#13: Re: Merging/Joining AoA

Posted on 2008-04-24 05:02:51 by Tad J McClellan

benkasminbullock@gmail.com <benkasminbullock@gmail.com> wrote:
> nolo contendere <simon.chao@fmr.com> wrote:
>
>> I'm not sure how much control you have over the structure of the data,
>> but it seems to me that you would be better served if the data were
>> stored in hashes to begin with:
>
> If the person needs to know how to put in a screw, why tell him he
> would be better served by using nails and a hammer?


Errr, because he would be better served, of course.


Q: I need to put a lot of screws in to hold the shingles on the roof.
Can anyone suggest a good power screwdriver?

A: You would be better served by using nails and a nail gun.


If you use screws it will take you 2 days to finish instead of 1 day.

Even worse, when you need to maintain your roof, it will take you
4 days to remove the old one instead of 1 day if you had used nails.



Choice of an approriate data structure is very important in designing
a software solution. (It made this task into a one-liner.)

If you don't have a choice of data structure, then you must
bite the bullet and write 10 or 20 lines of code.

nolo gave an appropriate predicate to his advice.

Seems clear enough that the advice should be skipped if the predicate
is not true...


--
Tad McClellan
email: perl -le "print scalar reverse qq/moc.noitatibaher\100cmdat/"

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#14: Re: Merging/Joining AoA

Posted on 2008-04-24 05:16:13 by benkasminbullock

Tad J McClellan <tadmc@seesig.invalid> wrote:

>> If the person needs to know how to put in a screw, why tell him he
>> would be better served by using nails and a hammer?
>
>
> Errr, because he would be better served, of course.
>
>
> Q: I need to put a lot of screws in to hold the shingles on the roof.
> Can anyone suggest a good power screwdriver?
>
> A: You would be better served by using nails and a nail gun.

Since I have no idea what the original poster's task was, why
speculate about it?

> Choice of an approriate data structure is very important in designing
> a software solution. (It made this task into a one-liner.)
>
> If you don't have a choice of data structure, then you must
> bite the bullet and write 10 or 20 lines of code.

My original solution had ten lines of code, it's true. But if you want
to reduce the lines of code, it's perfectly possible:

my %ak = (map{$$_[0],$_} @a);
my %bk = (map{$$_[0],$_} @b);
for (sort keys %ak) {my $v=$bk{$_}; push @c, [@{$ak{$_}}, @$v[1..$#$v]] if $v}
unshift @c, pop @c; # Just for Harmut Camphausen

That has the disadvantage of being less clear to read but it does
exactly the same thing.

If I was doing this for real I'd be much more worried about
problems such as empty values in the first column of the array, or
duplicate IDs in @a, or what to do with values which are in @a but not
in @b or vice-versa, than I would be about turning the whole thing into
a hash keyed by the values on the first line. That could just as
easily make other parts of the program more complicated, and it seems
to me that Perl programmers should be able to write code to deal with
arrays of arrays without getting confused, or write a regular
expression to match single quoted strings.

So I'm not sure what the point of the original advice was. To me it's
just confusing the issue.

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