%%
%?Programmed?by?Taesam?Lee??Dec.032009
%?INRS-ETE?Quebec?Canada
function?[Z]=SPI（Datascalenseas）
%Standardized?Precipitation?Index?
%?Input?Data
%?Data?:?Monthly?Data?vector?not?matrix?（monthly?or?seasonal?precipitation）
%?scale?:?131248
%?nseas?:?number?of?season?（monthly=12）
%?Example
%?Z=SPI（gamrnd（1110001）312）;?3-monthly?scale?
%?Notice?that??the?rest?of?the?months?of?the?fist?year?are?removed.
%?eg.?if?scale?=3?fist?year?data?3-12?SPI?values?are?not?estimated.

%if?row?vector?then?make?coloumn?vector
%if?（sz==1）?Data（:1）=Data;end
erase_yr=ceil（scale/12）;

%?Data?setting?to?scaled?dataset
A1=[];
for?is=1:scale?A1=[A1Data（is:length（Data）-scale+is）];end
XS=sum（A12）;

if（scale>1）?XS（1:nseas*erase_yr-scale+1）=[];???end

for?is=1:nseas
????tind=is:nseas:length（XS）;
????Xn=XS（tind）;
????[zeroa]=find（Xn==0）;
????Xn_nozero=Xn;Xn_nozero（zeroa）=[];
????q=length（zeroa）/length（Xn）;
????parm=gamfit（Xn_nozero）;
????Gam_xs=q+（1-q）*gamcdf（Xnparm（1）parm（2））;
????Z（tind）=norminv（Gam_xs）;
end

%Gamma?parameter?estimation?and?tranform

?屬性????????????大小?????日期????時間???名稱
-----------?---------??----------?-----??----
?????文件????????1098??2018-02-09?20:46??SPI.m
?????目錄???????????0??2018-02-09?20:47??__MACOSX\
?????文件?????????670??2018-02-09?20:46??__MACOSX\._SPI.m