Perl: Create a hash from an array - arrays

If I have the following array
my #header_line = ('id', 'name', 'age');
How do I create a hash from it equivalent to the line below?
my %fields = { id => 0, name => 1, age => 2};
The reason I want to do this is so that I can use meaningful names rather than magic numbers for indexes. For example:
$row->[$fields{age}]; # rather than $row->[2]


my %fields;
#fields{#header_line} = (0 .. $#header_line);


my %fields = map { $header_line[$_] => $_ } 0..$#header_line;


You said in reply to a comment that this is coming from Text::CSV. This module has a way to import this into a hash for you.
$csv->column_names( #header_line );
$row = $csv->getline_hr( $FH );
print $row->{ 'id' };


my %fields = ();
for (my $i = 0; $i < scalar(#header_line); $i++) {
$fields{$header_line[$i]} = $i;
}


TIMTOWTDI
my %fields = ();
foreach my $field(#header_line)
{
$fields{$field} = scalar(keys(%fields));
}

Related

Unable to find if one item exists in array of items and return the necessary message in Perl

I have array of IDs. I have one ID which I want to find if that ID exists in the array of IDs in Perl
I tried the following code:
my $ids = [7,8,9];
my $id = 9;
foreach my $new_id (#$ids) {
if ($new_id == $id) {
print 'yes';
} else {
print 'no';
}
}
I get the output as:
nonoyes
Instead I want to get the output as only:
yes
Since ID exists in array of IDs
Can anyone please help ?
Thanks in advance

my $ids = [7,8,9];
my $id = 9;
if (grep $_ == $id, #ids) {
print $id. " is in the array of ids";
} else {
print $id. " is NOT in the array";
}

You just need to remove the else part and break the loop on finding the match:
my $flag = 0;
foreach my $new_id (#$ids) {
if ($new_id == $id) {
print 'yes';
$flag = 1;
last;
}
}
if ($flag == 0){
print "no";
}
Another option using hash:
my %hash = map { $_ => 1 } #$ids;
if (exists($hash{$id})){
print "yes";
}else{
print "no";
}

use List::Util qw(any); # core module
my $id = 9;
my $ids = [7,8,9];
my $found_it = any { $_ == $id } #$ids;
print "yes" if $found_it;

The following piece of code should cover your requirements
use strict;
use warnings;
my $ids = [7,8,9];
my $id = 9;
my $flag = 0;
map{ $flag = 1 if $_ == $id } #$ids;
print $flag ? 'yes' : 'no';
NOTE: perhaps my #ids = [7,8,9]; is better way to assign an array to variable

How can i get top 15 occurrences in an array and use each value to fetch data from mysql database?

I am currently working on a project (A music website) with PHP Codeigniter. I want to fetch top 15 songs by number of downloads. To my knowledge, I got all unique ID's out ranging from highest to least. But now, I want to use each of these unique ID's to fetch data from another table in the database.
I have tried using for loop; but it seems to only return one of the rows which happens to be the first and highest number of occurrence in the array. The code below echo's the ID's but how can I use each of those ID's to fetch data.
function top15(){
$this->db->select('musiccode');
$result=$this->db->get('downloads');
$query = $result->result_array();
$downloads = array();
if(!empty($query)) {
foreach($query as $row)
{
$musiccode[] = $row['musiccode'];
}
$mode = array_count_values($musiccode);
arsort($mode);
$i = 0;
foreach ($mode as $field => $number) {
$i++;
echo $field." occured ". $number." times <br>";
if ($i == 15) {
break;
}
}
}
}
for ($b=0; $b < count($field); $b++) {
$this->db->where(array('track_musiccode'=> $field));
$field = $this->db->get('tracks');
return $field->result_array();
}
The code above only produce one row for me. I expect to have more than one and according to the number of ID's in the array. Thanks in advance.

For a single column condition, you could use where_in() instead and drop the for loop :
$this->db->where_in('track_musiccode', $field);
$field = $this->db->get('tracks');
return $field->result_array();

Yes Finally i did it. Incase if anyone needs it. this works just fine
function top15(){
$this->db->where('d_month', date('m'));
$this->db->select('musiccode');
$result=$this->db->get('downloads');
$query = $result->result_array();
$downloads = array();
if(!empty($query)) {
foreach($query as $row){
$musiccode[] = $row['musiccode'];
}
$res='';
$count=array_count_values($musiccode);
arsort($count);
$keys=array_keys($count);
for ($i=0; $i < count($keys); $i++) {
$res[] .= "$keys[$i]";
}
$this->db->where_in('track_musiccode', $res);
return $this->db->get('tracks')->result_array();
}
}

And I got this too. If I wasn't going to count occurrences but just iterate the number of downloads which is far more better than counting in other not to over populate the database and make your website work slowly.
function top15(){
$tracks = '';
$this->db->group_by('counter');
$result=$this->db->get('downloads');
$query = $result->result_array();
$counter = '';
$fields = '';
if(!empty($query)) {
foreach($query as $row) {
$counter[] = $row['counter'];
}
rsort($counter);
for ($i=0; $i<=15; $i++) {
$this->db->where('downloads.counter', $counter[$i]);
$this->db->join('tracks', 'tracks.musicid = downloads.musicid');
$fields[] = $this->db->get('downloads')->row_array();
}
return $fields;
}
}
Enjoy...

Array to string conversion in foreach

Hi,
I am getting an array for string conversion when using the code below:
$sort_order = array();
foreach (getAll() as $field) {
$sort_order[$field->name] = query("SELECT sort_order
FROM field_table
WHERE field_name = '$field->name'");
$o->tag[$field->name] = $field->title. $sort_order[$field->name];
}
The error says there is an Array to string conversion in line 6. Why is that?
Thank you.

query will return an array, so you need to do something like:
$result = query("SELECT sort_order
FROM field_table
WHERE field_name = '$field->name'");
$row = $result->fetch_assoc();
sort_order[$field->name] = $row['sort_order'];

Yes because the query returns an array, which is directly assigned to the variable. Please try this :
$sort_order = array();
foreach (getAll() as $field) {
$result = query("SELECT sort_order
FROM field_table
WHERE field_name = '$field->name'");
while($res = $result->fetch_array()) {
$sort_order = $res['sort_order'];
}
$o->tag[$field->name] = $field->title.$sort_order;
}

Perl: Comparing 2 hash of arrays with another array

I have written the code below in Perl but it's not giving the desirable output. I am dealing with the comparison between one array and two hash of arrays.
Given sample input files:
1) file1.txt
A6416 A2318
A84665 A88
2) hashone.pl
%hash1=(
A6416=>['E65559', 'C11162.1', 'c002gnj.3',],
A88=>['E77522', 'M001103', 'C1613.1', 'c001hyf.2',],
A84665=>['E138347', 'M032578', 'C7275.1', 'c009xpt.3',],
A2318=>['E128591', 'C43644.1', 'C47705.1', 'c003vnz.4',],
);
3) hashtwo.pl
%hash2=(
15580=>['C7275.1', 'E138347', 'M032578', 'c001jnm.3', 'c009xpt.2'],
3178=>['C1613.1', 'E77522','M001103', 'c001hyf.2', 'c001hyg.2'],
24406=>['C11162.1', 'E65559', 'M003010', 'c002gnj.2'],
12352=>['C43644.1', 'C47705.1', 'E128591','M001458', 'c003vnz.3'],
);
My aim is to achieve the task described:
From file1.txt, I have to locate the corresponding ID in %hash1. For instance,A6416 (file1.txt) is the key in %hash1. Next, I have to find the values of A6416 ['E65559', 'C11162.1', 'c002gnj.3',] in %hash2. If majority (more than 50%) of the values are found in %hash2, I replace A6416 with corresponding key from %hash2.
Example:
A6416 A2318
A84665 A88
Output:
24406 12352
15580 3178
Please note that the keys for %hash1 and %hash2 are different (they don't overlap). But the values are the same (they overlap).
#!/usr/bin/perl -w
use strict;
use warnings;
open FH, "file1.txt" || die "Error\n";
my %hash1 = do 'hashone.pl';
my %hash2 = do 'hashtwo.pl';
chomp(my #array=<FH>);
foreach my $amp (#array)
{
if ($amp =~ /(\d+)(\s?)/)
{
if (exists ($hash1{$1}))
{
for my $key (keys %hash2)
{
for my $i ( 0 .. $#{ $hash2{$key} } )
{
if ((#{$hash1{$1}}) eq ($hash2{$key}[$i]))
{
print "$key";
}
}
}
}
}
}
close FH;
1;
Any guidance on this problem is highly appreciated. Thank you!

I think you should invert %hash2 into this structure:
$hash2{'C7275.1'} = $hash2{'E138347'} = $hash2{'M032578'}
= $hash2{'c001jnm.3'} = $hash2{'c009xpt.2'} = 15580;
$hash2{'C1613.1'} = $hash2{'E77522'} = $hash2{'M001103'}
= $hash2{'c001hyf.2'} = $hash2{'c001hyg.2'} = 3178;
$hash2{'C11162.1'} = $hash2{'E65559'}
= $hash2{'M003010'} = $hash2{'c002gnj.2'} = 24406;
$hash2{'C43644.1'} = $hash2{'C47705.1'} = $hash2{'E128591'}
= $hash2{'M001458'} = $hash2{'c003vnz.3'} = 3178;
So that you can perform these look-ups much more effectively, rather than having to iterate over every element of every element of %hash2.

Building on the responses from ruakh and zock here is the code you need to build the look-up table for hash2
#!/usr/bin/perl
use strict;
use warnings;
use Data::Dumper;
my %hash2=(
15580=>['C7275.1', 'E138347', 'M032578', 'c001jnm.3', 'c009xpt.2'],
3178=>['C1613.1', 'E77522','M001103', 'c001hyf.2', 'c001hyg.2'],
24406=>['C11162.1', 'E65559', 'M003010', 'c002gnj.2'],
12352=>['C43644.1', 'C47705.1', 'E128591','M001458', 'c003vnz.3'],
);
# Build LUT for hash2
my %hash2_lut;
foreach my $key (keys %hash2)
{
foreach my $val (#{$hash2{$key}})
{
$hash2_lut{$val} = $key
}
}
print Dumper(\%hash2_lut);
Please select ruakh's post as the answer, just trying to clarify the code for you. Use Data::Dumper...it is your friend.
Here is the output:
$VAR1 = {
'C47705.1' => '12352',
'M032578' => '15580',
'E138347' => '15580',
'E77522' => '3178',
'C7275.1' => '15580',
'c001jnm.3' => '15580',
'E65559' => '24406',
'C1613.1' => '3178',
'M001458' => '12352',
'c002gnj.2' => '24406',
'c009xpt.2' => '15580',
'c001hyf.2' => '3178',
'C43644.1' => '12352',
'E128591' => '12352',
'c001hyg.2' => '3178',
'M003010' => '24406',
'c003vnz.3' => '12352',
'C11162.1' => '24406',
'M001103' => '3178'
};

Array Manipulation join with out split

#browser = ("NS", "IE", "Opera");
my $add_str = "Browser:";
$count = 0;
foreach (#browser) {
my $br = $_;
$browser[$count] = "$add_str:$br";
$count++ ;
}
is there any other way to do this ? best way ?

You could use map.
#browser = ("NS", "IE", "Opera");
my $add_str = "Browser";
#browser = map { "${add_str}:$_"; } #browser;

In Perl 5, the for loop aliases each item, so you can simply say
#!/usr/bin/perl
use strict;
use warnings;
my #browsers = qw/NS IE Opera/;
my $add_str = "Browser:";
for my $browser (#browsers) {
$browser = "$add_str:$browser";
}
print join(", ", #browsers), "\n";

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