Matlab多项式拟合

Question

I want a vector of -2 to 2 in a step size of 0.5 which would be saved as x. Next i want y as y=3*x^3+3*x+6.

When i do x=linspace(-2,3,9) i get

-2.0000   -1.5000   -1.0000   -0.5000         0    0.5000    1.0000    1.5000    2.0000

But still the compiler complains : Error using ^

Incorrect dimensions for raising a matrix to a power. Check that the matrix is square and the power is a scalar. To perform elementwise matrix powers, use '.^'.

Answer 1

You need the elementwise .^ operation (see Error message). There are two types of operations in matlab. The usual vectorwise operations (*, /, ^) and their elementwise counterparts (.*, ./, .^).

When working with scalars this does not matter, but as soon as you run on vectors or matrices the operation changes.

Look here for a more in depth explanation.

Answer 2

Just use a dot(.) before the power sign.It's because you are using the power sign to the whole matrix and you need to do the element-wise operation.

x=linspace(-2,3,9)
y=3*x.^3+3*x+6