help mata mm_locate()
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Title

    mm_locate() -- Search an ordered vector


Syntax

          void  mm_locate(y, x, j)

          void  mm_hunt(y, x, j)

    where

            y:  numeric vector containing data; y must be ordered, either
                ascending or descending

            x:  numeric scalar containing value to be located in y

            j:  real scalar containing initial guess for mm_hunt(); will be
                replaced by a real scalar such that x lies between y[j] and
                y[j+1]


Description

    Given an ordered data vector y and some value x, mm_locate(), replaces j
    such that x lies between y[j] and y[j+1]. j==0 or j==length(y) is
    returned, if x is out of range. mm_locate() applies the bisection method
    to locate x in y.

    mm_hunt() also locates x in y. However, mm_hunt() uses the input value of
    j as the starting point for the search process and applies a modified
    algorithm.  mm_hunt() is useful if consecutive searches be performed for
    similar values.

    mm_locate() is a translation of the locate algorithm in Press et al.
    (1992:117). mm_hunt() is a translation of the hunt algorithm in Press et
    al. (1992:118-119).


Remarks

    None.


Conformability

    mm_locate(y, x, j),
    mm_hunt(y, x, j):
    input:
           y:  n x 1 or 1 x n
           x:  1 x 1
           j:  1 x 1
    output:
           j:  1 x 1


Diagnostics

    None.


Source code

    mm_locate.mata


References

    Press, William H., Saul A. Teukolsky, William T. Vetterling, Brian P.
        Flannery (1992). Numerical Recipes in C. The Art of Scientific
        Computing. Second Edition. Cambridge University Press.  
        http://www.numerical-recipes.com/


Author

    Ben Jann, ETH Zurich, jann@soz.gess.ethz.ch


Also see