print the first and the last element of an hash 1

[Jurafsky]

Hello all! I've a csv file like :


City sunshine Temperature
Ajaccio 2790 14.7
Lyon 2072 11.4
Marseille 2763 14.2
Brest 1729 10.8
Lille 1574 9.7
Paris 1833 11.2
Strasbourg 1685 9.7

I'd like to print just the city+temperature with the highest and the lowest temperature. How?

#!/usr/bin/perl
use warnings;
use diagnostics;
use Data::Dumper;
$Data::Dumper::Terse = 1;
$Data::Dumper::Indent = 0;
 

#definyn arrays for temperatures, files and city
my (@temp, @file, @ville);
my ($file, $line);
my %temperature;

$file = "temperatures.csv";
#I don't consider the first line of the file and I put just the city and  its temperture in two arrays

open (F, "<", $file);
while(defined($line = <F>)) {
if ( $. > 1 ) {
	@file = split(/ /, $line);
	push(@ville, $file[0]);
	push(@temp, $file[2]);
	}
}

#then I create the hash and print what  there's inside

@temperature{@ville} = @temp;
print '%temperature : ', Dumper(\%temperature), "\n";

#now I "order" the hash by value 
foreach my $value (sort {$temperature{$a} <=> $temperature{$b} || ($a cmp $b) } keys %temperature) 
{
     print " the city of $value and its temperature : $temperature{$value}\n";
}


close(F);

#is there a way to print ONLY the first and the last element in order to have the highest and the lowest temperature?

 

[prex1]

If you need the hash for other purposes

my@tord;
@tord=sort{$temperature{$a}<=>$temperature{$b}}keys%temperature;
print 'The city of $tord[0] and its minimum temperature : ',$temperature{$tord[0]},"\n";
print 'The city of $tord[-1] and its maximum temperature : ',$temperature{$tord[-1]},"\n";

otherwise

my($maxt,$mint,$temp,$maxv,$minv,$ville)=(-1e300,1e300);
open(F,$file);
$line=<F>;
while(<F>){
  ($ville,undef,$temp)=split;
  if($temp>$maxt){
    $maxt=$temp;
    $maxv=$ville;
  }
  if($temp<$mint){
    $mint=$temp;
    $minv=$ville;
  }
}
print 'The city of $minv and its minimum temperature : ',$mint,"\n";
print 'The city of $maxv and its maximum temperature : ',$maxt,"\n";

Franco

http://www.xcalcs.com

: Online engineering calculations

http://www.megamag.it

: Magnetic brakes for fun rides

http://www.levitans.com

: Air bearing pads

 

[Jurafsky]

Thank you (Grazie!),

I found this

$regex .= $t9{$num};

in an exercice. What is ".=" and how is it called? This is the first time I've seen it.

 

[prex1]

Just like [tt]$a+=$b[/tt] means sum $b to $a and store the result in $a, [tt]$a.=$b[/tt] means append string $b to string $a and store the result in $a.

http://www.xcalcs.com

: Online engineering calculations

http://www.megamag.it

: Magnetic brakes for fun rides

http://www.levitans.com

: Air bearing pads

 

[Jurafsky]

Thank you! now is clear!

$regex .=$t9{$t};

it's the same as...

$regex = $regex.$t9{$t}; !