Locate maximum occuring element array in perl

AI Thread Summary
To extract the maximum occurring element in an array using Perl, the discussion emphasizes the use of hashes for counting occurrences. A sample code snippet demonstrates how to create a hash that tracks the frequency of each element in the array. The code initializes an array and iterates through it, incrementing the count for each value in the hash. To find the maximum value and its occurrences, sorting the hash values is suggested. Additionally, participants discuss how to print all elements with their respective occurrence counts, including filtering to show only those that occur more than twice. The final code example illustrates how to iterate over the hash keys and conditionally print values based on their occurrence count. Overall, the conversation provides practical insights into effectively using Perl for array manipulation and frequency counting.
paanz
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guys..i need help...

how to extract a maximum occurring element in array using perl...

example...

a[1]=11;
a[2]=12;
a[3]=13;
a[4]=14;
a[5]=15;
a[6]=13;
a[7]=14;
a[8]=14;


we will see that, 14 is the most occurring at element 8...
how to know the no of frequently it occur?example above 14 is 3...

really need your help...
 
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I'm not quite sure what you're asking-- you want to know that 14 is the most occurring element, but then you say "at 8", which implies that you also want to know the index at which it becomes true? I'm not sure.

Also, this isn't quite Perl-- or, not good Perl. For one, you don't have $ signs before each array element, and you're also using a variable name of "a", which is a special variable (actually, $a is special, @a isn't, but it's not a good idea to use them). Also, you start your array at 1, rather than 0, which means that you want to skip undefined values?

Either way, this is simple with hashes. For your example:

Code:
#!perl
my(@a) = (undef,11,12,13,14,15,13,14,14);
my(%count);
foreach my $value (@a) {
    $count{$value}++;
}
$max_value = (sort {$count{$b} <=> $count{$a}} @a)[0];
print "Max value = $max_value, occurrs $count{$max_value} times\n";

If you want to know the index at which this happened, it's a little more involved, but not too hard:

Code:
#!perl
my(@a) = (undef,11,12,13,14,15,13,14,14);
my(%count,$max);
for(my $i=1; $i<@a;$i++) {
    $count{$a[$i]}++;
    if($count{$a[$i]} > $count{$a[$max]}) { $max = $i; }
}
print "Max value = $a[$max], occurrs $count{$a[$max]} times, surpasses at index $max\n";

DaveE
 
thanks davee...

all I am saying is just an example...im not give the proper example which is I am sorry...

btw...thanks ur answer...
im just wondering...

how if I am want to print all the element in that array with showing the max occur...

like this...

my(@a) = (undef,11,12,13,14,15,13,14,14);11= 1 occurence
12=1 occurence
13=2 occurence
14=3 occurence
15=1 occurence

im still new in perl...need ur help guys...
 
thanks davee...

all I am saying is just an example...im not give the proper example which is I am sorry...

btw...thanks ur answer...
im just wondering...

how if I am want to print all the element in that array with showing the max occur...

like this...

my(@a) = (undef,11,12,13,14,15,13,14,14);


11= 1 occurence
12=1 occurence
13=2 occurence
14=3 occurence
15=1 occurence

im still new in perl...need ur help guys...
 
The above code is already tracking that information in the hashes. This part right here:

Code:
foreach my $value (@a) {
    $count{$value}++;
}

That takes each value in the @a array, and assigns it to an entry in the %count hash. Each time the value is encountered in the array, it increments the count of that value by 1. After that loop is complete, you can reference $count{12} and it will be set to 1, or $count{14} and it will be set to 3. So you can loop through a series of values and print out (for instance) $count{$value}, and it will print out the number of occurrences of each element.

If you don't want to print out any instances that occur 0 times, you can either wrap them in an if statement, or you can iterate over the (keys %count) array, which will ONLY return the values that have occurrences in the hash.

DaveE
 
davee123 said:
The above code is already tracking that information in the hashes. This part right here:

Code:
foreach my $value (@a) {
    $count{$value}++;
}

That takes each value in the @a array, and assigns it to an entry in the %count hash. Each time the value is encountered in the array, it increments the count of that value by 1. After that loop is complete, you can reference $count{12} and it will be set to 1, or $count{14} and it will be set to 3. So you can loop through a series of values and print out (for instance) $count{$value}, and it will print out the number of occurrences of each element.

If you don't want to print out any instances that occur 0 times, you can either wrap them in an if statement, or you can iterate over the (keys %count) array, which will ONLY return the values that have occurrences in the hash.

DaveE



if i want to print out the occurence more than 2 times only,u said i can iterate over the (keys %count) array...

i still don get it...

is it like this...

if (keys %count > 2){print $count{$value};}
 
paanz said:
if i want to print out the occurence more than 2 times only,u said i can iterate over the (keys %count) array...

It would be like:

Code:
foreach my $value (keys %count) {
  if($count{$value} > 2) {
    print "$value occurred $count{$value} times!\n";
  }
}

DaveE
 
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