Mudanças entre as edições de "Uso do calculo simbólico na Matlab"
Linha 17: | Linha 17: | ||
=[http://www.mathworks.com/help/symbolic/formula-rearrangement-and-rewriting.html Formula Rearrangement and Rewriting]= | =[http://www.mathworks.com/help/symbolic/formula-rearrangement-and-rewriting.html Formula Rearrangement and Rewriting]= | ||
− | :*[http://www.mathworks.com/help/symbolic/numden.html numden - Extract numerator and denominator | + | :*[http://www.mathworks.com/help/symbolic/numden.html numden] - Extract numerator and denominator |
syms s | syms s | ||
H = (s^2 + 5*s + 6)/(s^4 + 7*s + 27) | H = (s^2 + 5*s + 6)/(s^4 + 7*s + 27) | ||
− | + | ||
− | + | H = | |
+ | (s^2 + 5*s + 6)/(s^4 + 7*s + 27) | ||
+ | |||
[N,D] = numden(H) | [N,D] = numden(H) | ||
− | + | ||
− | + | N = | |
− | + | s^2 + 5*s + 6 | |
− | + | D = | |
− | :*[http://www.mathworks.com/help/symbolic/coeffs.html coeffs - Coefficients of polynomial | + | s^4 + 7*s + 27 |
+ | :*[http://www.mathworks.com/help/symbolic/coeffs.html coeffs] - Coefficients of polynomial | ||
Coefficients of Univariate Polynomial - Find the coefficients of this univariate polynomial. | Coefficients of Univariate Polynomial - Find the coefficients of this univariate polynomial. | ||
n = coeffs(N) | n = coeffs(N) | ||
− | + | ||
− | + | n = | |
− | + | [ 1, 5, 6] | |
+ | '''Atenção!!!''' Os termos nulos não são inseridos no vetor dos coeficientes. | ||
[d,terms] = coeffs(D) | [d,terms] = coeffs(D) | ||
− | + | ||
− | + | d = | |
− | + | [ 1, 7, 27] | |
− | + | terms = | |
+ | [ s^4, s, 1] | ||
+ | |||
+ | :*[http://www.mathworks.com/help/symbolic/sym2poly.html sym2poly] - Extract vector of all numeric coefficients, including zeros, from symbolic polynomial | ||
+ | Para extrair o vetor com os termos nulos use sym2poly. | ||
+ | n = sym2poly(N) | ||
+ | |||
+ | n = | ||
+ | 1 5 6 | ||
+ | d = sym2poly(D) | ||
+ | |||
+ | d = | ||
+ | 1 0 0 7 27 |
Edição das 14h40min de 3 de junho de 2016
Use subs to Evaluate Expressions and Functions
Evaluation is one of the most common mathematical operations. Therefore, it is important to understand how and when Symbolic Math Toolbox™ performs evaluations. For example, create a symbolic variable, x, and then assign the expression x^2 to another variable, y.
syms x y = x^2;
Now, assign a numeric value to x.
x = 2;
This second assignment does not change the value of y, which is still x^2. If later you change the value of x to some other number, variable, expression, or matrix, the toolbox remembers that the value of y is defined as x^2. When displaying results, Symbolic Math Toolbox does not automatically evaluate the value of x^2 according to the new value of x.
y
y = x^2
To enforce evaluation of y according to the new value of x, use the subs function.
subs(y)
ans = 4
Formula Rearrangement and Rewriting
- numden - Extract numerator and denominator
syms s H = (s^2 + 5*s + 6)/(s^4 + 7*s + 27)
H = (s^2 + 5*s + 6)/(s^4 + 7*s + 27)
[N,D] = numden(H)
N = s^2 + 5*s + 6 D = s^4 + 7*s + 27
- coeffs - Coefficients of polynomial
Coefficients of Univariate Polynomial - Find the coefficients of this univariate polynomial.
n = coeffs(N)
n = [ 1, 5, 6]
Atenção!!! Os termos nulos não são inseridos no vetor dos coeficientes.
[d,terms] = coeffs(D)
d = [ 1, 7, 27] terms = [ s^4, s, 1]
- sym2poly - Extract vector of all numeric coefficients, including zeros, from symbolic polynomial
Para extrair o vetor com os termos nulos use sym2poly.
n = sym2poly(N)
n = 1 5 6 d = sym2poly(D)
d = 1 0 0 7 27