undefined X variable in curve fit

hello,

I have returned to the optimisation, I get

f(x) = p1*x^7 + p2*x^6 + p3*x^5 + p4*x^4 + p5*x^3 + p6*x^2 + p7*x + p8

Undefined function or variable 'x'.

how must I redefine X?

Thanks.

Answer 1

[Walter Roberson]

f = @(x) p1*x^7 + p2*x^6 + p3*x^5 + p4*x^4 + p5*x^3 + p6*x^2 + p7*x + p8

or

f = polyval([p1, p2, p3, p4, p5, p6, p7, p8], x);

Answer 2

[Gavin Seddon]

I had tried the 1st, I think it is my installation. Thanks.