如何在Matlab中绘制三角函数和其他阶梯函数

Question

正如标题所示，我想知道如何在Matlab中绘制三角函数。 e.g。

f(x) = 1-|x| for |x| < 1 and f(x) = 0 otherwise

以及功能：

Af(x) = A for x >= 0 and Af(x) = 0 for x < 0; -f(x) = -1 for x >= 0 and -f(x) = 0 for x < 0

Answer 1

我假设你没有使用符号变量。对于matlab中的2D绘图，您需要两个相等大小的矢量，每个轴一个，因此您需要创建一个x轴矢量和y轴矢量。在你的例子中f（x）= 1- | x | for | x | ＆LT; 1你可以这样做：

x = linspace(-5,5,500); %x-axis vector from -5 to 5 with 500 points
y = zeros(1,500);  %y-axis vector initialized to 0, also 500 points like the x-axis vector
y(abs(x) < 1) = 1- abs(x(abs(x)<1)); %the points corresponding to |x|< 1 are set to |x|

figure() %new figure
plot(x,y) %plot
box off  %removing box
grid on  %adding grid
xlabel('x axis', 'FontSize', 15) %label of x axis
ylabel('y axis', 'FontSize', 15) %label of y axis
axis([x(1), x(end), -0.5, 1.5])  %axis limits

有了这样你就得到了这样的情节：

对于其他功能，你必须像这一个一样，建立x轴向量和y轴向量。

更新：在另一个示例中：f(x) = A for x >= 0 and f(x) = 0 for x < 0：

A = 3;
x = linspace(-5,5,500); %x-axis vector from -5 to 5 with 500 points
y = zeros(1,500);  %y-axis vector initialized to 0, also 500 points like the x-axis vector
y(x >= 0) = A; %the points corresponding to x >= 0 are set to A

figure() %new figure
plot(x,y) %plot
box off  %removing box
grid on  %adding grid
xlabel('x axis', 'FontSize', 15) %label of x axis
ylabel('y axis', 'FontSize', 15) %label of y axis
axis([x(1), x(end), -0.5, 3.5])  %axis limits