Undefined Offset PHP
===

I am receiving the following error when I try to execute my code. 
Notice (8): Undefined offset:  18 [APP/libs/excel_adapters/coverage.php, line 12]
Notice (8): Undefined offset:  23 [APP/libs/excel_adapters/coverage.php, line 13]
Notice (8): Undefined offset:  24 [APP/libs/excel_adapters/coverage.php, line 14]
Notice (8): Undefined offset:  25 [APP/libs/excel_adapters/coverage.php, line 15]
Notice (8): Undefined offset:  26 [APP/libs/excel_adapters/coverage.php, line 16]
Notice (8): Undefined offset:  14 [APP/libs/excel_adapters/coverage.php, line 17]
Notice (8): Undefined offset:  14 [APP/libs/excel_adapters/coverage.php, line 18]

With that said, this code is used to upload a spreadsheet to a database. I think my problem is with the $s variable. If someone would please take a look at my code and tell me what my problem is. I think a fresh set of eyes would help me tremendously. 

          <?php 
          class CoverageExcelAdapter {

	    public function extract($s, $args = array()) { 
		App::import('component', 'CakeSession');        
		$userId = CakeSession::read('Auth.User.id');		
		$ret = array();
		
		$ret['Coverage'] = array(
			'name' => $s[0][12][3], 
			'effective_date' => $this->Date->formatDate($s[0][18][3]),
			'expiration_date' => $this->Date->formatDate($s[0][18][6]),
			'broker_first_name' => ucwords($s[0][23][3]),
			'broker_middle_initial' => strtoupper(substr($s[0][24][3], 0, 1)),
			'broker_last_name' => ucwords($s[0][25][3]),
			'broker_suffix' => ucwords($s[0][26][3]),
			'producing_id' => $this->State->stateStrToId($s[0][14][3]), 
			'filing_id' => $this->State->stateStrToId($s[0][14][6]),
