Filling in missing values in an array

[dhuang90]

Hello Monks, I have been given a large array of numbers, but there are missing values which have a value of NULL. I am to write a program which takes the NULL values and copies the closest value in the array. If a missing value is equidistant between two values, then it will take the average of the two arrays. To illustrate (let underscores represent NULL values: 4 _ _ _ 5 The first NULL would take the value 4, the third NULL takes the value 5, and the middle NULL takes the value 4.5 The code I have written is below, but it doesn't appear to change anything. Any ideas to get me moving? Thanks monks

$left  = 1; #measures the distance to the left to the first non-NULL v
+alue
$right = 1; #measures the distance to the right to the first non-NULL 
+value
$q = 0; #used to iterate through the exposures for the first time
$p = 0; #used to find a non-NULL value to the left, first iteration
$k = 0; #used to find a non-NULL value to the right, first iteration
$m = 0; #used to iterate through the exposures for the second time
$n = 0; #used to find a non-NULL value to the left, second iteration
$l = 0; #used to find a non-NULL value to the right, second iteration
$o = 0; #used to assign values using an average, third iteration

foreach $exp (@exposures) {
    if ($exp eq "NULL") {
        while ($exposures[$q - $p] eq "NULL") {
        ++$left;
        ++$p;
        }
        while($exposures[$q + $k] eq "NULL") {
        ++$right;
        ++$k;
        }
    }
    if ($left < $right) {
        $data{$q} = "L";
    }
    if ($left > $right) {
        $data{$q} = "R";
    }
    $left = 1;
    $right = 1;
    $p = 0;
    $k = 0;
    ++$q;
}
 
 $end = $#exposures;
 $number_of_exposures = $end + 1;
 
while ($m <= $number_of_exposures) {
    if ($data{$m} eq "L") {
        while ($exposures[$m - $n] eq "NULL") {
            ++$n; 
            }
            $exposures[$m] = $exposures[4];
            }
    if    ($data{$m} eq "R") {
        while ($exposures[$m + $l] eq "NULL"){
            ++$l;
            }
            $exposures[$m] = $exposures[4];
        }
    $n = 0;
    $l = 0;
    ++$m;
}

foreach $exp (@exposures) {
    if ($exp eq "NULL") {
    $exp = ($exposures[$o - 1] + $exposures[$o + 1])/2;
    }
    ++$o;
}