/**
* TBILLYIELD
*
* Returns the yield for a Treasury bill.
*
* @param mixed settlement The Treasury bill's settlement date.
* The Treasury bill's settlement date is the date after the issue date when the Treasury bill is traded to the buyer.
* @param mixed maturity The Treasury bill's maturity date.
* The maturity date is the date when the Treasury bill expires.
* @param int price The Treasury bill's price per $100 face value.
* @return float
*/
public static function TBILLYIELD($settlement, $maturity, $price)
{
$settlement = Functions::flattenSingleValue($settlement);
$maturity = Functions::flattenSingleValue($maturity);
$price = Functions::flattenSingleValue($price);
// Validate
if (is_numeric($price)) {
if ($price <= 0) {
return Functions::NAN();
}
if (Functions::getCompatibilityMode() == Functions::COMPATIBILITY_OPENOFFICE) {
++$maturity;
$daysBetweenSettlementAndMaturity = DateTime::YEARFRAC($settlement, $maturity) * 360;
if (!is_numeric($daysBetweenSettlementAndMaturity)) {
// return date error
return $daysBetweenSettlementAndMaturity;
}
} else {
$daysBetweenSettlementAndMaturity = DateTime::getDateValue($maturity) - DateTime::getDateValue($settlement);
}
if ($daysBetweenSettlementAndMaturity > 360) {
return Functions::NAN();
}
return (100 - $price) / $price * (360 / $daysBetweenSettlementAndMaturity);
}
return Functions::VALUE();
}
