function?p?=?stblpdf（xalphabetagamdeltavarargin）
%P?=?STBLPDF（XALPHABETAGAMDELTA）?returns?the?pdf?of?the?stable?
%?distribtuion?with?characteristic?exponent?ALPHA?skewness?BETA?scale
%?parameter?GAM?and?location?parameter?DELTA?at?the?values?in?X.??We?use?
%?the?parameterization?of?stable?distribtuions?used?in?[2]?-?The?
%?characteristic?function?phi（t）?of?a?S（ALPHABETAGAMDELTA）
%?random?variable?has?the?form
%
%?phi（t）?=?exp（-GAM^ALPHA?|t|^ALPHA?[1?-?i?BETA?（tan（pi?ALPHA/2）?sign（t）]
%??????????????????+?i?DELTA?t?）??if?alpha?~=?1
%
%?phi（t）?=?exp（-GAM?|t|?[?1?+?i?BETA?（2/pi）?（sign（t））?log|t|]?+?i?DELTA?t
%?????????????????????????????????if?alpha?=?1
%
%?The?size?of?P?is?the?size?of?X.??ALPHABETAGAM?and?DELTA?must?be?scalars
%?
%P?=?STBLPDF（XALPHABETAG