Chapter 6
Computer Algebra
6.1 Matlab’s Symbolic Toolbox
Matlab’s Symbolic Toolbox is a collection of functions that provide access
to some of Maple’s functionality. Using this toolbox, one can create sym
objects, which represent expressions, and perform symbolic operations on
them, such as differentiation, integration, or analytical solution techniques
for equations.
6.1.1 Creating Symbolic objects
The sym function creates a new Matlab object that represents an expression,
similar to an expression in Maple. It accepts as an argument a string repre-
senting the expression, and returns an ob ject whose value is that expression.
An optional second argument can be used to set properties of the ex-
pression, such as whether the expression is assumed to be a real number, or
a positive number.
Instead of a string, one may pass a matrix to sym, in which case a sym-
bolic representation of the matrix is created. An optional second argument
indicates how the floating-point entries are to be represented symbolically.
The argument ’f’ is used to create a floating-point representation, ’r’ for a
rational representation (the default), ’d’ for decimal, and ’e’ for “estimate
error”, which implies ’r’ but also provides an estimate of the error in the
rational approximation.
>> myexpr=sym(’x’)
myexpr =
201
