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Numerical Integration to Infinity
Syntax int2inf(function fvec, low, eps)
See Also gaussq , gaussleg

Description
Returns an approximation for
      +inf
     /
     | f(x) dx
     /
     low
where low is a real or double-precision scalar. Given a column vector xvec of length n and with the same type as low, the function fvec returns the column vector
     /          \
     | f(xvec ) |
     |       1  |
     | f(xvec ) |
     |       2  |
     |    ...   |
     | f(xvec ) |
     \       n  /
The relative accuracy for the integral is specified by eps which is a scalar with the same type as low . If the approximation converges, the return value is a scalar with the same type as low. Otherwise, the return value has type equal to "novalue".

Example
If you enter
     clear
     function fvec(xvec) begin
          return exp(-xvec)
     end
     low  = 0.
     eps  = 1e-5
     int2inf(function fvec, low, eps)
 O-Matrix will reply
     1
 which is equal to the integral of exp(-x) from zero to infinity.

Reference
This integration method assumes that
            2
     f(x)  x  -->  0  as x --> +infinity