M文件举例

    为了演示If-Else-End结构，考虑精通MATLAB工具箱中函数mmono，它检查一个向量的单调性。

                   » mmono(1:12)     %  strictly increasing input

                   ans =

                        2

                   » mmono([1:12  12  13:24])     %  non decreasing input

                   ans =

                        1

                   » mmono([1  3  2  -1])     %  not monotonic in any sense

                   ans =

                        0

                   » mmono([12:-1:0  0  -1])     %  non increasing

                   ans =

                       -1

                   » mmono(12:-1:0)     %  strictly decrasing

                   ans =

                       -2

这个精通MATLAB工具箱的函数主体给出如下：

          function f=mmono(x)

          %  MMONO Test for monotonic vector.

          %  MMONO(x) where x is a vector return:

          %    2 if x is strictly increasing,

          %    1 if x is non decreasing,

          %   -1 if x is non increasing,

          %   -2 if x is strictly decreasing,

          %    0 otherwise.

          %  Copyright (c) 1996 by Prentice-Hall,Inc.

          x=x(:);        %  make x a column vector

          y=diff(x);      %  find differences between consecutive elements

          if all(y>0)      %  test for strict first

                     f=2;

          elseif all(y>=0)

                     f=1;

          elseif all(y<0)   %  test for strict first

                     f=-2;

          elseif all(y<=0) 

                     f=-1;

          else

                     f=0;   %  otherwise response

          end

    函数mmono直接利用了If-Else-End结构。由于严格单调是一般单调的子集，首先检验严格的单调是必要的，因为在所碰见的第一个真值分支里，其语句执行之后，结构就结束。