Re: deleting duplicates in array using references

On 30 Jul, 19:46, Paul Lalli <mri...@xxxxxxxxx> wrote:
On Jul 30, 2:37 pm, billb <billbea...@xxxxxxx> wrote:

i have a multidimensional array, but i want to delete duplicate
entries based on the first element of each 'row'.

$ perldoc -q duplicate
Found in /opt2/Perl5_8_4/lib/perl5/5.8.4/pod/perlfaq4.pod
How can I remove duplicate elements from a list or array?

my array is:

my @array = ( [UK9004411, A140, B, 0.040] , [UK0030239, H7140, H,
0.030] , [UK0030239, S1393, M1, 0.030] , [UK0012821, H4030, H,
0.010] , [UK0012821, H4060, H, 0.010] );

and I want to end up with
( [UK9004411, A140, B, 0.040] , [UK0030239, H7140, H, 0.030] ,
[UK0012821, H4030, H, 0.010] )

(no real preference in which row is dropped...just on a first come
first served basis.)

i.e. take out the duplicate codes based on the first element of each
row $array[$row] -> [0]

$ perl -MData::Dumper -e'
my @array = (
[UK9004411, A140, B, 0.040] ,
[UK0030239, H7140, H, 0.030] ,
[UK0030239, S1393, M1, 0.030] ,
[UK0012821, H4030, H, 0.010] ,
[UK0012821, H4060, H, 0.010] ,
);
my %seen;
my @nodups = grep { !$seen{$_->[0]}++ } @array;
print Dumper(\@nodups);
'
$VAR1 = [
[
'UK9004411',
'A140',
'B',
'0.04'
],
[
'UK0030239',
'H7140',
'H',
'0.03'
],
[
'UK0012821',
'H4030',
'H',
'0.01'
]
];

i looked into splice() function based on the index but not sure this
is the best way or the syntax for this?

splice (@array , $row, 1); ?

splice() is fine for removing the elements once you know which ones
you want to remove, but it's useless for actually finding which
elements to remove.

Paul Lalli

ah, very simple and very fast as well! I'll have to understand how
this is working. It uses a hash I see. Many thanks.

.

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