perl - 为什么 Perl 的 GD::Graph 提示 "Invalid data set"？

Question

我正在为我的作业编写一个 Perl 小程序，我是 Perl 的新手。

我编写的代码为我提供了我需要的完全相同的值，但我在创建条形图时遇到此错误。

Invalid data set: 0 at line 67

第 67 行在下面的代码中用注释标记。

存储在x轴的值是:

40 44 48 52 64 76 83 104 105 148 149 249 431 665 805 1420 1500 

y_axis 是:

16 1  1 6 1 1 1 1 1 1 1 1 1 1 1 2 5 

这是我的代码:

use GD::Graph::bars;

open(CHECKBOOK,"c:\\Perl\\bin\\ip_packet_trace1.txt");

my $counter = -1;
my @sizearray = {};
while ($record = <CHECKBOOK>) {
    @array = split(/\t/,$record);
    $counter++;
    $sizearray[$counter] = $array[6];

}

$counter++;

my @array1 = sort {$a <=> $b} @sizearray;
print "$counter\n";
print "@array1\n";


my @freq = {0...0};

foreach $elem (@array1){

    my $s = $freq[$elem]+1;

    $freq[$elem] = $s;
}


my $size = @freq;
my @x_axis = {};
my @y_axis = {};

my $count2 = -1;


for($i = 1; $i < $size; $i++){

    my $elem = $freq[$i];

    if($elem  and $elem > 0  ){

        $count2++;

        $x_axis[$count2] =  $i;

        $y_axis[$count2] = $elem;
    }

}


print "@x_axis \n";
print "@y_axis \n";




my $mygraph = GD::Graph::bars->new(500, 300); # line 67

$mygraph->set(x_label     => 'Month',

y_label     => 'Number of Hits',

title       => 'Number of Hits in Each Month in 2002',

) or warn $mygraph->error;

my @data = {@x_axis,@y_axis};



my $myimage = $mygraph->plot(\@data) or die $mygraph->error;

open(IMG, '>C:\\image\\file.gif') or die $!;

binmode IMG;

print IMG $myimage->gif;

close IMG;

Answer 1

我认为你对 @data 的分配可能是罪魁祸首。

my @data = {@x_axis,@y_axis};

这将创建一个只有一个元素的数组。那一个元素是一个散列。 GD::Graph文档显示您需要一个数组数组。正如 daotoad 所述，这就是 Data::Dumper派上用场。尝试以下操作:

use Data::Dumper;
my @x_axis = 1...100;
my @y_axis = "a"..."z";
my @data = {@x_axis,@y_axis};
warn Dumper(\@data);

您可以看到数据是如何被解释的，并且看到它与 GD::Graph example 不同。 :

@data = ( 
    ["1st","2nd","3rd","4th","5th","6th","7th", "8th", "9th"],
    [    1,    2,    5,    6,    3,  1.5,    1,     3,     4],
    [ sort { $a <=> $b } (1, 2, 5, 6, 3, 1.5, 1, 3, 4) ]
  );