/* TEST FOR HETEROSCEDASTICITY AND TECHNICAL INEFFICENCY */

/* Load Data and Define Variables */
load path = c:\gauss35\classes\econ5340\data\;
load x[464,30] = tescores.txt;
tescore = x[.,2];
modern = x[.,3];
experience = x[.,4];
gender = x[.,5];
age = x[.,6];
elemed = x[.,7];
seced = x[.,8];
somecollege = x[.,9];
college = x[.,10];
prof = x[.,11];
plots = x[.,12];
crops = x[.,13];
erosion = x[.,14];
fertility = x[.,15];
aptitude = x[.,16];
slope = x[.,17];
pests = x[.,18];
weeddens = x[.,19];
weedhght = x[.,20];
plantdis = x[.,21];
hydromorph = x[.,22];
lowland = x[.,23];
irrigated = x[.,24];
raindays = x[.,25];
rainqty = x[.,26];
region2 = x[.,27];
region3 = x[.,28];
yr94 = x[.,29];
yr95 = x[.,30];
nobs = rows(x);
constant = ones(nobs,1);

y = -ln(tescore);
xmat = constant~modern~modern^2~experience~experience^2~gender~age~age^2~elemed~
        seced~somecollege~college~prof~plots~plots^2~crops~crops^2~erosion~fertility~
        aptitude~slope~slope^2~pests~pests^2~weeddens~weeddens^2~weedhght~weedhght^2~
        plantdis~plantdis^2~hydromorph~lowland~irrigated~raindays~raindays^2~
        rainqty~rainqty^2~region2~region3~yr94~yr95;
k = cols(xmat);
vnum = seqa(1,1,k);

/* OLS Regression */
b = inv(xmat'*xmat)*(xmat'*y);
resid = y - xmat*b;
sigmahat2 = (resid'*resid)/nobs;

/* Breusch-Pagan Test */
z = constant~region2~region3;
g = (resid.*resid/sigmahat2) - 1;
LM = (g'*z*inv(z'*z)*z'*g)/2;
print "LM Statistic for BP Hd Test = " LM;