linearize

linearize returns the linearization of the polynomial \(p(x)\) at the point value(x). It is based on the command jacobian

Syntax

h = linearize(p)

Examples

The linearization is performed at the current value of x

x = sdpvar(1,1);
f = x^2;
assign(x,1);
sdisplay(linearize(f))
ans =
    '-1+2*x'

assign(x,3);
sdisplay(linearize(f))
ans =
    '-9+6*x'

The command is short for

sdisplay(value(f)+value(jacobian(f,x))*(x-value(x)))
ans =
    '-9+6*x'

The command applies to matrices as well

p11 = sdpvar(1,1);p12 = sdpvar(1,1);
P = [p11 p12;p12 1];
assign(P,[3 2;2 1])
sdisplay(linearize(P*P))
ans =

    '-13+6*p11+4*p12'    '-6+2*p11+4*p12'
    '-6+2*p11+4*p12'     '-3+4*p12'