symvar - Find symbolic variables in symbolic expression or matrix

Syntax

symvar(s) symvar(s,n)

Description

symvar(s) returns a vector containing all the symbolic variables in s. The variables are returned in the alphabetical order with uppercase letters preceding lowercase letters. If there are no symbolic variables in s, then symvar returns the empty vector. symvar does not consider the constants pi, i, and j to be variables.

symvar(s,n) returns a vector containing the n symbolic variables in s that are alphabetically closest to 'x':

The variables are sorted by the first letter in their names. The ordering is x y w z v u ... a X Y W Z V U ... A. The name of a symbolic variable cannot begin with a number.
For all subsequent letters, the ordering is alphabetical, with all uppercase letters having precedence over lowercase: 0 1 ... 9 A B ... Z a b ...z.

Note symvar(s) can return variables in different order than symvar(s,n).

Examples

syms wa wb wx yx ya yb
f = wa + wb + wx + ya + yb + yx;
symvar(f)

The result is:

ans =
[ wa, wb, wx, ya, yb, yx]

syms x y z a b
w = x^2/(sin(3*y - b));
symvar(w)

The result is:

ans =
[ b, x, y]

symvar(w, 3)

The result is:

ans =
[ x, y, b]

symvar(s,1) returns the variable closest to x. When performing differentiation, integration, substitution or solving equations, MATLAB uses this variable as a default variable.

syms v z
g = v + z;
symvar(g, 1)

The result is:

ans =
z

syms aaa aab
g = aaa + aab;
symvar(g, 1)

The result is:

ans =
aaa

syms X1 x2 xa xb
g = X1 + x2 + xa + xb;
symvar(g, 1)

The result is:

ans =
x2

symvar - Find symbolic variables in symbolic expression or matrix

Syntax

Description

Examples

See Also

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