heaviside 函数在 ezplot 和 fplot 中产生不同的输出 [英] heaviside function procudes different outputs in ezplot and fplot

问题描述

我是 MATLAB 新手，我正在尝试使用 heaviside() 绘制阶跃函数.我首先尝试了以下代码:

I'm new to MATLAB and I'm trying to plot a step function with heaviside(). I tried at first the following code:

f = @(x)heaviside(x+2) - heaviside(x-2);
fplot(f, [-10 10])

结果:

使用ezplot，结果和我想的一样:

With ezplot, the result is as I thought:

f = @(x)heaviside(x+2) - heaviside(x-2);
ezplot(f, [-10 10])

结果:

fplot 和 ezplot 有什么区别?提前致谢！

What is the difference between fplot and ezplot? Thanks in advance!

推荐答案

这与 fplot 文档的以下部分有关:

This pertains to the following bit of fplot documentation:

fplot 使用自适应步长控制来生成代表性图形，将其评估集中在函数变化率最大的区域.

fplot uses adaptive step control to produce a representative graph, concentrating its evaluation in regions where the function's rate of change is the greatest.

它看到您的函数几乎在任何地方都是常数，并且不在 [-2 2] 之间求值.解决方案是指定最少数量的评估点:

It sees that your function is constant just about everywhere and doesn't evaluate between [-2 2]. The solution is to specify a minimum number of evaluation points:

n = 1e3;
fplot(f, [-10 10],n)

例如，如果我们从 fplot 得到输出坐标:

For example, if we get the output coordinates from fplot:

>> [x,y] = fplot(f, [-10 10]);
>> [x y]

ans =

  -10.0000         0
   -9.9600         0
   -9.8800         0
   -9.7200         0
   -9.4000         0
   -8.7600         0
   -7.4800         0
   -4.9200         0
   -2.3600         0
    2.7600         0
   10.0000         0

您可以看到正在运行的自适应评估.它从 -10 开始，越来越快地前进，直到它从 -2.36 跳到 +2.76！在数据提示上看到:

You can see the adaptive evaluation in action. It starts at -10, steps forward faster and faster until it skips right from -2.36 to +2.76! Seen on datatips:

如果我们使用 n=1e3 评估点:

If we use n=1e3 evaluation points:

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