Simple curves are polynomials of various degrees, or orders. The degree is the integer of the highest exponent in the expression. The illustrations are as follows:
A MATLAB represents a polynomial as a row vector of coefficients. For illustration, the polynomial x3 + 2x2 - 4x + 3 would be represented by the vector [1 2 -4 3].
The polynomial 2x4 - x2 + 5 would be represented by [2 0 -1 0 5]; note that the zero terms for x3 and x1.
There are built-in functions sym2poly and poly2sym which convert symbolic expressions to polynomial vectors and vice versa, the illustration is as shown below:
>> myp = [1,2,-4,3];
>> mypoly = [2 0 -1 0 5];
2 0 -1 0 5