错误使用 tf (line 299) The values of the "Numerator" and "Denominator" properties must be row vectors or cell arrays of row vectors, where each vector is nonempty and containing numeric data. Type "help tf.num" or "help tf.den" for more information. 出错 a (line 11) tf_sys = tf(num, den);

根据错误提示，MATLAB 报错的原因是分子和分母多项式的格式不正确。在您提供的代码中，使用 `ss2tf` 函数得到的分子和分母多项式可能不是行向量形式，或者其中包含非数值数据。

为了解决这个问题，可以使用 `squeeze` 函数将多维数组压缩为行向量。同时，使用 `num2str` 函数将分子和分母多项式转化为字符串，方便查看其内容。代码如下：

A = [0 1 0 0; -0.6 0 0.4 0; 0 0 0 1; 0.4 0 -1 0];
B = [0 0; 0.2 0; 0 0; 0 0.2];
C = [1 0 0 0; 0 0 1 0];
D = [0 0; 0 0];

[num, den] = ss2tf(A, B, C, D, 1);
num_str = num2str(squeeze(num));
den_str = num2str(squeeze(den));
tf_sys = tf(num, den);

这样，得到的分子和分母多项式就是行向量形式的字符串，可以方便地查看其内容了。

相关问题

The values of the "Numerator" and "Denominator" properties must be row vectors or cell arrays of row vectors, where each vector is nonempty and containing numeric data. Type "help tf.num" or "help tf.den" for more information. 出错 a (line 16) tf_sys = tf(num, den);

根据错误提示，MATLAB报错是因为传递函数的分子和分母多项式不是行向量或行向量的 cell 数组，每个向量都必须包含数值数据，而不能包含其他类型的数据。

解决这个问题，可以将分子和分母多项式转换为行向量形式，使用 MATLAB 的 `reshape` 函数将结果重新变形为行向量。代码如下：

A = [0 1 0 0; -0.6 0 0.4 0; 0 0 0 1; 0.4 0 -1 0];
B = [0 0; 0.2 0; 0 0; 0 0.2];
C = [1 0 0 0; 0 0 1 0];
D = [0 0; 0 0];

[num, den] = ss2tf(A, B, C, D, 1);
num = reshape(num.', 1, []);
den = reshape(den.', 1, []);
tf_sys = tf(num, den);

这里，使用 `reshape` 和转置操作将多项式向量变形为行向量形式。然后，将变形后的分子和分母多项式作为参数传递给 `tf` 函数，得到转换后的传递函数模型 `tf_sys`。

Create a class called Rational for performing arithmetic with fractions. Use integer variables to represent the private data of the class – the numerator and the denominator. Provide a constructor that enables an object of this class to be initialized when it’s declared. The constructor should store the fraction in reduced form. For example, the fraction 2/4 would be stored in the object as 1 in the numerator and 2 in the denominator. In order to compute the reduced form, you need to write a reduction function which uses the Euclidean algorithm to get the greatest common divisor (GCD) of the numerator and denominator first and then divides GCD to get the reduced numerator and denominator. Provide public member functions that perform each of the following tasks: (a) Subtract a Rational number from the other Rational number. The result should be stored in reduced form. (b) Divide a Rational number by the other Rational number. The result should be stored in reduced form. (c) Print Rational numbers in the form a/b, where a is the numerator and b is the denominator. (d)Compare two Rational numbers to make sure which one is smaller or they are equal. (1 for the first number, 2 for the second number and 0 if they are equal) Please also write a main function to prompt the user to input two Rational numbers . Subtract one number from the other from these two numbers using (a) and then print the result using (c). Divide one number from the other from these two numbers using (b) and then print the result using (c). Compare these two Rational numbers using (d) and indicate which one is smaller or they are equal. 用c++5.11寫出，且使用using namespace std;

以下是符合要求的C++ 代码：

#include <iostream>
using namespace std;

class Rational {
private:
    int numerator, denominator;
    int gcd(int a, int b) {
        if (b == 0) return a;
        return gcd(b, a % b);
    }
public:
    Rational(int num = 0, int den = 1) {
        int divisor = gcd(num, den);
        numerator = num / divisor;
        denominator = den / divisor;
    }
    Rational operator- (Rational other) {
        int num = numerator * other.denominator - other.numerator * denominator;
        int den = denominator * other.denominator;
        return Rational(num, den);
    }
    Rational operator/ (Rational other) {
        int num = numerator * other.denominator;
        int den = denominator * other.numerator;
        return Rational(num, den);
    }
    void print() {
        cout << numerator << "/" << denominator;
    }
    int compare(Rational other) {
        int num1 = numerator * other.denominator;
        int num2 = other.numerator * denominator;
        if (num1 < num2) return 1;
        if (num1 > num2) return 2;
        return 0;
    }
};

int main() {
    Rational r1, r2;
    cout << "Enter the first rational number (numerator denominator): ";
    cin >> r1;
    cout << "Enter the second rational number (numerator denominator): ";
    cin >> r2;
    Rational diff = r1 - r2;
    cout << "The difference is ";
    diff.print();
    cout << endl;
    Rational quotient = r1 / r2;
    cout << "The quotient is ";
    quotient.print();
    cout << endl;
    int result = r1.compare(r2);
    if (result == 1) {
        cout << "The first number is smaller." << endl;
    } else if (result == 2) {
        cout << "The second number is smaller." << endl;
    } else {
        cout << "The two numbers are equal." << endl;
    }
    return 0;
}

请注意，此代码使用了重载运算符-和/来实现两个Rational数的减法和除法。此外，它还定义了一个比较函数来比较两个Rational数的大小。在主函数中，我们首先提示用户输入两个Rational数，然后执行所需的操作并输出结果。