在Matlab中画出函数f(x)=1/(1+ⅇ^(-x) )及其导数在同一坐标轴上的图像
时间: 2023-06-24 07:05:18 浏览: 83
可以使用Matlab的plot函数来绘制函数和导数的曲线。具体步骤如下:
1. 定义函数f(x)和其导数f'(x)。
```matlab
syms x
f = 1/(1+exp(-x));
df = diff(f,x);
```
2. 生成x轴上的数据点。
```matlab
x_vals = linspace(-10,10,1000);
```
3. 计算函数f(x)和导数f'(x)在x轴上的取值。
```matlab
f_vals = eval(subs(f,x,x_vals));
df_vals = eval(subs(df,x,x_vals));
```
4. 绘制函数f(x)和导数f'(x)的曲线。
```matlab
plot(x_vals,f_vals,'LineWidth',2); hold on;
plot(x_vals,df_vals,'LineWidth',2);
legend('f(x)','f''(x)');
xlabel('x');
ylabel('y');
```
完整代码如下:
```matlab
syms x
f = 1/(1+exp(-x));
df = diff(f,x);
x_vals = linspace(-10,10,1000);
f_vals = eval(subs(f,x,x_vals));
df_vals = eval(subs(df,x,x_vals));
plot(x_vals,f_vals,'LineWidth',2); hold on;
plot(x_vals,df_vals,'LineWidth',2);
legend('f(x)','f''(x)');
xlabel('x');
ylabel('y');
```
绘制结果如下图所示:
![函数和导数的曲线](https://i.imgur.com/KcJk6lM.png)