displayFormula
Display symbolic formula from string
Description
displayFormula(
displays the symbolic
formula from the string symstr
)symstr
without evaluating the operations. All
workspace variables that are specified in symstr
are replaced by their
values.
Examples
Multiplication Formula of Matrix and Scalar
Create a 3-by-3 matrix. Multiply the matrix by the scalar coefficient K^2
.
syms K A A = [-1, 0, 1; 1, 2, 0; 1, 1, 0]; B = K^2*A
B =
The result automatically shows the multiplication being carried out element-wise.
Show the multiplication formula without evaluating the operations by using displayFormula
. Input the formula as a string. The variable A
in the string is replaced by its values.
displayFormula("F = K^2*A")
Multiplication Formula of Matrix and Vector
Create a 3-by-3 matrix and a 3-by-1 vector. Create a symbolic equation that multiplies the matrix and the vector.
syms A [3 3] syms v B [3 1] eqn = B == A*v
eqn =
The result shows the multiplication being carried out where the elements of the matrix and the vector are combined.
Show the multiplication formula without combining the elements by using displayFormula
. Input the formula as a string.
displayFormula("B == A*v")
Display Differential Equation
Define a string that describes a differential equation.
S = "m*diff(y,t,t) == m*g-k*y";
Create a string array that combines the differential equation and additional text. Display the formula along with the text.
symstr = ["'The equation of motion is'"; S;"'where k is the elastic coefficient.'"]; displayFormula(symstr)
Display and Evaluate Symbolic Expression
Create a string S
representing a symbolic expression.
S = "exp(2*pi*i)";
Create another string symstr
that contains S
.
symstr = "1 + S + S^2 + cos(S)"
symstr = "1 + S + S^2 + cos(S)"
Display symstr
as a formula without evaluating the operations by using displayFormula
. S
in symstr
is replaced by its value.
displayFormula(symstr)
To evaluate the strings S
and symstr
as symbolic expressions, use str2sym
.
S = str2sym(S)
S =
expr = str2sym(symstr)
expr =
Substitute the variable S
with its value by using subs
. Evaluate the result in double precision using double
.
double(subs(expr))
ans = 3.5403
Display and Solve Quadratic Equation
Define a string that represents a quadratic formula with the coefficients a
, b
, and c
.
syms a b c k symstr = "a*x^2 + b*x + c";
Display the quadratic formula, replacing a
with k
.
displayFormula(symstr,a,k)
Display the quadratic formula again, replacing a
, b
, and c
with 2
, 3
, and -1
, respectively.
displayFormula(symstr,[a b c],[2 3 -1])
To solve the quadratic equation, convert the string into a symbolic expression using str2sym
. Use solve
to find the zeros of the quadratic equation.
f = str2sym(symstr); sol = solve(f)
sol =
Use subs
to replace a
, b
, and c
in the solution with 2
, 3
, and -1
, respectively.
solValues = subs(sol,[a b c],[2 3 -1])
solValues =
Input Arguments
symstr
— String representing symbolic formula
character vector | string scalar | cell array of character vectors | string array
String representing a symbolic formula, specified as a character vector, string scalar, cell array of character vectors, or string array.
You can also combine a string that represents a symbolic formula with regular text (enclosed in single quotation marks) as a string array. For an example, see Display Differential Equation.
old
— Expression or variable to be replaced
character vector | string scalar | cell array of character vectors | string array | symbolic variable | symbolic function | symbolic expression | symbolic array
Expression or variable to be replaced, specified as a character vector, string scalar, cell array of character vectors, string array, symbolic variable, function, expression, or array.
new
— New value
number | character vector | string scalar | cell array of character vectors | string array | symbolic number | symbolic variable | symbolic expression | symbolic array
New value, specified as a number, character vector, string scalar, cell array of character vectors, string array, symbolic number, variable, expression, or array.
Version History
Introduced in R2019b
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