Just curious if this is possible. I have some data on different countries that i have stored in a multidimensional array called data[][]. What I want to do is sort data[][] by population which happens to be stored in data[i][4] where i is the index to iterate from country to country.

I would like something like this:

sort!("a>b")(data[][4]);

Anybody have any suggestions?

On Wednesday, 22 October 2014 at 00:32:56 UTC, neal wrote:
> Just curious if this is possible. I have some data on different countries that i have stored in a multidimensional array called data[][]. What I want to do is sort data[][] by population which happens to be stored in data[i][4] where i is the index to iterate from country to country.
>
> I would like something like this:
>
> sort!("a>b")(data[][4]);
>
> Anybody have any suggestions?

More like this:
sort!(a.country > b.country)(data[][4]);

On Wednesday, 22 October 2014 at 00:36:22 UTC, Joel wrote:
> On Wednesday, 22 October 2014 at 00:32:56 UTC, neal wrote:
>> Just curious if this is possible. I have some data on different countries that i have stored in a multidimensional array called data[][]. What I want to do is sort data[][] by population which happens to be stored in data[i][4] where i is the index to iterate from country to country.
>>
>> I would like something like this:
>>
>> sort!("a>b")(data[][4]);
>>
>> Anybody have any suggestions?
>
> More like this:
> sort!(a.country > b.country)(data[][4]);

Oops, forgot the quotes: sort!("a.country > b.country")(data[][4]);

neal:

> Anybody have any suggestions?

Something like this, perhaps?

data.sort!q{ a[4] > b[4] };

Bye,
bearophile

On Wednesday, 22 October 2014 at 01:02:17 UTC, bearophile wrote:
> neal:
>
>> Anybody have any suggestions?
>
> Something like this, perhaps?
>
> data.sort!q{ a[4] > b[4] };
>
> Bye,
> bearophile

Hmmm.. Im getting some interesting results here. So when i put
all of the populations in an area and used this code:

sort!("a>b")(population);
writeln("Top 5 population in 1993: ");
for(int i = 0; i < 5;i++)
     writeln(population[i]);


I get:

Top 5 population in 1993:
1189550675
916529257
264493898
191658591
156810428


The problem there is that i lose the country that the population
is associated with (the top one being China).

When I run your code:

data.sort!q{ a[4] > b[4] };
for(int i = 0; i < 5; i++)
    writeln(data[][]);

I get this result for the top 5:

["Portugal", "1593140", "-668536", "1993", "9993683", "8"]
["Anguilla", "114", "-536", "1993", "9865", "10"]
["Malawi", "31745", "-25289", "1993", "9862531", "6"]
["Grenada", "2274", "-4890", "1993", "96908", "2"]
["Burkina Faso", "22613", "-38738", "1993", "9688261", "6"]


Notice that the top populations arent correct.

On Wednesday, 22 October 2014 at 01:58:19 UTC, neal wrote:
> On Wednesday, 22 October 2014 at 01:02:17 UTC, bearophile wrote:
>> neal:
>>
>>> Anybody have any suggestions?
>>
>> Something like this, perhaps?
>>
>> data.sort!q{ a[4] > b[4] };
>>
>> Bye,
>> bearophile
>
> Hmmm.. Im getting some interesting results here. So when i put
> all of the populations in an area and used this code:
>
> sort!("a>b")(population);
> writeln("Top 5 population in 1993: ");
> for(int i = 0; i < 5;i++)
>      writeln(population[i]);
>
>
> I get:
>
> Top 5 population in 1993:
> 1189550675
> 916529257
> 264493898
> 191658591
> 156810428
>
>
> The problem there is that i lose the country that the population
> is associated with (the top one being China).
>
> When I run your code:
>
> data.sort!q{ a[4] > b[4] };
> for(int i = 0; i < 5; i++)
>     writeln(data[][]);
>
> I get this result for the top 5:
>
> ["Portugal", "1593140", "-668536", "1993", "9993683", "8"]
> ["Anguilla", "114", "-536", "1993", "9865", "10"]
> ["Malawi", "31745", "-25289", "1993", "9862531", "6"]
> ["Grenada", "2274", "-4890", "1993", "96908", "2"]
> ["Burkina Faso", "22613", "-38738", "1993", "9688261", "6"]
>
>
> Notice that the top populations arent correct.


Wow sorry I just realized my mistake. the array is an array of strings!

data.sort!q{ to!int(a[4]) > to!int(b[4]) };

This code fixes my problem! Thanks for the quick responses guys. you rock!

neal:

> data.sort!q{ to!int(a[4]) > to!int(b[4]) };
>
> This code fixes my problem! Thanks for the quick responses guys. you rock!

That converts string->int many more than once for each string. So if memory is not a problem, consider using a decorate-sort-undecorate pattern:

data.schwartzSort!q{ a[4].to!int };

Bye,
bearophile

On Wednesday, 22 October 2014 at 07:38:01 UTC, bearophile wrote:
> neal:
>
>> data.sort!q{ to!int(a[4]) > to!int(b[4]) };
>>
>> This code fixes my problem! Thanks for the quick responses guys. you rock!
>
> That converts string->int many more than once for each string. So if memory is not a problem, consider using a decorate-sort-undecorate pattern:
>
> data.schwartzSort!q{ a[4].to!int };
>
> Bye,
> bearophile

Interesting! Thank you. Memory isn't a problem but I would still
like to learn how to write more efficient programs. If i posted
my code would you be able to give me some advice?

Neal:

> Interesting! Thank you. Memory isn't a problem

Unfortunately currently the sort-decorate-undercorate in Phobos is not very fast.


> but I would still
> like to learn how to write more efficient programs. If i posted
> my code would you be able to give me some advice?

There is far more than just me around here. If you post code, someone usually can write come comment.

Bye,
bearophile