function?[Bx?By?Bz]?=?igrf（time?latitude?longitude?altitude?coord）

%?IGRF?Earth‘s?magnetic?field?from?IGRF?model.
%?
%?Usage:?[BX?BY?BZ]?=?IGRF（TIME?LATITUDE?LONGITUDE?ALTITUDE?COORD）
%?????or?[BX?BY?BZ]?=?IGRF（COEFS?LATITUDE?LONGITUDE?ALTITUDE?COORD）
%?????or?B?=?IGRF（TIME?LATITUDE?LONGITUDE?ALTITUDE?COORD）
%?????or?B?=?IGRF（COEFS?LATITUDE?LONGITUDE?ALTITUDE?COORD）
%?
%?Calculates?the?components?of?the?Earth‘s?magnetic?field?using?the
%?International?Geomagnetic?Reference?Field?（IGRF）?model.?The?inputs?for
%?the?position?can?be?scalars?or?vectors?（in?the?latter?case?each?should
%?have?the?same?number?of?elements?or?be?a?scalar）?but?TIME?must?be?a
%?scalar.
%?
%?When?all?the?coordinate?inputs?are?scalars?the?function?can?be?run?more
%?efficientl