Here's a generalization of a snippet I posted earlier (which, BTW, had a my bug, now fixed); it does both maxima and minima: 

use strict;
my $input_file = 'foobar.txt';
open my $in, $input_file or die "Failed to read $input_file: $!\n";

my @max = do { local $_ = <$in>; chomp; [ split ] };
my @min = ( [ @{ $max[ 0 ] } ] );

my $last = $max[ 0 ][ 1 ];

while ( <$in> ) {
  chomp;
  my ( $x, $y ) = split;
  if ( $y > $last ) {
    $max[ -1 ] = [ $x, $y ];
  }
  elsif ( $max[ -1 ] ) {
    $max[ @max ] = undef;
  }
  if ( $y < $last ) {
    $min[ -1 ] = [ $x, $y ];
  }
  elsif ( $min[ -1 ] ) {
    $min[ @min ] = undef;
  }
  $last = $y;
}
close $in;

pop @max unless $max[ -1 ];
pop @min unless $min[ -1 ];

print "Maxima:\n";
print "($_->[ 0 ], $_->[ 1 ])\n" for @max;

print "Minima:\n";
print "($_->[ 0 ], $_->[ 1 ])\n" for @min;
__END__
Maxima:
(4.133, 4580.870000)
(4.160, 4544.999000)
(4.413, 2473.469000)
(4.547, 2663.464000)
(4.773, 2588.583000)
Minima:
(4.147, 4522.753000)
(4.307, 1094.119000)
(4.467, 2029.188000)
(4.680, 814.717000)

[download]

the lowliest monk

In reply to Re^3: Any idea for predicting the peak points in the graph by perl by tlm
in thread Any idea for predicting the peak points in the graph by perl by Anonymous Monk

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