RosettaCodeData/Task/Numerical-integration/Stata/numerical-integration.stata

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mata
function integrate(f,a,b,n,u,v) {
s = 0
h = (b-a)/n
m = length(u)
for (i=0; i<n; i++) {
x = a+i*h
for (j=1; j<=m; j++) s = s+v[j]*(*f)(x+h*u[j])
}
return(s*h)
}
function log_(x) {
return(log(x))
}
function id(x) {
return(x)
}
function cube(x) {
return(x*x*x)
}
function inv(x) {
return(1/x)
}
function test(f,a,b,n) {
return(integrate(f,a,b,n,(0,1),(1,0)),
integrate(f,a,b,n,(0,1),(0,1)),
integrate(f,a,b,n,(0.5),(1)),
integrate(f,a,b,n,(0,1),(0.5,0.5)),
integrate(f,a,b,n,(0,1/2,1),(1/6,4/6,1/6)))
}
test(&cube(),0,1,100)
test(&inv(),1,100,1000)
test(&id(),0,5000,5000000)
test(&id(),0,6000,6000000)
end