m文件的不同编程风格对程序的运行速度也有比较大的影响，下面的代码比较了采用for 循环关系运算赋值，for循环＋if 语句以及直接采用数组运算的运行速度。比较的结果第三种方法采用数组直接运算最快，第一种方法次之，第二种方法最慢。第一种方法的运行速度约为第三种方法的两到三倍，第二种方法为第三种方法的三到四倍。

具体在我的电脑中的一次运行结果为：0.28125秒，0.39063和0.09375。

function PerformanceComp()

Length = 10^7;

Source = round(rand(Length, 1)) * 2 - 1;

%% to evaluate the for loop time with memory allocation first

StartTime = cputime;

Res = zeros(Length, 1);

for i=1:Length

Res(i) = Source(i) >= 0;

end

EndTime = cputime;

Duration = EndTime - StartTime;

disp(['The for loop with memory allocation running time is ' num2str(Duration)]);

%% to evaluate the for loop time with memory allocation first

%  with if else clause

StartTime = cputime;

Res = zeros(Length, 1);

for i=1:Length

if Source(i) >= 0

Res(i) = 1;

else

Res(i) = 0;

end

end

EndTime = cputime;

Duration = EndTime - StartTime;

disp(['The for loop with memory allocation running time' ...

'with if clause is ' num2str(Duration)]);

%% to evaluate the array operation running time

StartTime = cputime;

Res = Source >= 0;

EndTime = cputime;

Duration = EndTime - StartTime;

disp(['The array operation time is ' num2str(Duration)]);