I have a problem with unwrap

I want to plot phase of a signal with unwrap code but when i run it, matlab shows me this error:

Error using sym/diff (line 36)
The second and third arguments must either be variables or a variable and a nonnegative integer
specifying the number of differentiations.

Error in unwrap>LocalUnwrap (line 85)
dp = diff(p,1,1);                % Incremental phase variations

Error in unwrap (line 65)
   q(indf,j) = LocalUnwrap(p(indf,j),cutoff);

Error in Q1 (line 40)
unwrap(phase_1)

How can I fix this problem?

Answer 1

[Walter Roberson]

unwrap() is only defined for numeric values, not for symbolic values.

[Ghazal Hnr]

phase_1 is numeric :

>> phase_1 = -atan(b_n_1,a_n_1)

phase_1 =

[ atan((100*cos(pi/25) + 25*5^(1/2) + 25)/(100*sin(pi/25) - 25*2^(1/2)*(5 - 5^(1/2))^(1/2))), atan((100*cos((2*pi)/25) - 25*5^(1/2) + 25)/(100*sin((2*pi)/25) + 25*2^(1/2)*(5^(1/2) + 5)^(1/2))) - pi, atan((100*cos((3*pi)/25) - 25*5^(1/2) + 25)/(100*sin((3*pi)/25) - 25*2^(1/2)*(5^(1/2) + 5)^(1/2))), atan((100*cos((4*pi)/25) + 25*5^(1/2) + 25)/(100*sin((4*pi)/25) + 25*2^(1/2)*(5 - 5^(1/2))^(1/2))) - pi, pi + atan((2^(1/2)*(5*5^(1/2) - 15))/(10*(5 - 5^(1/2))^(1/2))), atan((100*cos((6*pi)/25) + 25*5^(1/2) + 25)/(100*sin((6*pi)/25) - 25*2^(1/2)*(5 - 5^(1/2))^(1/2))) - pi, atan((100*cos((7*pi)/25) - 25*5^(1/2) + 25)/(100*sin((7*pi)/25) + 25*2^(1/2)*(5^(1/2) + 5)^(1/2))) - pi, atan((100*cos((8*pi)/25) - 25*5^(1/2) + 25)/(100*sin((8*pi)/25) - 25*2^(1/2)*(5^(1/2) + 5)^(1/2))), atan((100*cos((9*pi)/25) + 25*5^(1/2) + 25)/(100*sin((9*pi)/25) + 25*2^(1/2)*(5 - 5^(1/2))^(1/2))) - pi, pi + atan((2^(1/2)*(5*5^(1/2) - 25))/(10*(5^(1/2) + 5)^(1/2))), atan((100*cos((11*pi)/25) + 25*5^(1/2) + 25)/(100*sin((11*pi)/25) - 25*2^(1/2)*(5 - 5^(1/2))^(1/2))) - pi, pi + atan((100*cos((12*pi)/25) - 25*5^(1/2) + 25)/(100*sin((12*pi)/25) + 25*2^(1/2)*(5^(1/2) + 5)^(1/2))), pi - atan((100*cos((12*pi)/25) + 25*5^(1/2) - 25)/(100*sin((12*pi)/25) - 25*2^(1/2)*(5^(1/2) + 5)^(1/2))), atan((25*5^(1/2) - 100*cos((11*pi)/25) + 25)/(100*sin((11*pi)/25) + 25*2^(1/2)*(5 - 5^(1/2))^(1/2))) - pi, pi - atan((2^(1/2)*(5*5^(1/2) + 15))/(10*(5^(1/2) + 5)^(1/2))), atan((25*5^(1/2) - 100*cos((9*pi)/25) + 25)/(100*sin((9*pi)/25) - 25*2^(1/2)*(5 - 5^(1/2))^(1/2))) - pi, pi - atan((100*cos((8*pi)/25) + 25*5^(1/2) - 25)/(100*sin((8*pi)/25) + 25*2^(1/2)*(5^(1/2) + 5)^(1/2))), -atan((100*cos((7*pi)/25) + 25*5^(1/2) - 25)/(100*sin((7*pi)/25) - 25*2^(1/2)*(5^(1/2) + 5)^(1/2))), atan((25*5^(1/2) - 100*cos((6*pi)/25) + 25)/(100*sin((6*pi)/25) + 25*2^(1/2)*(5 - 5^(1/2))^(1/2))) - pi, pi - atan((2^(1/2)*(5*5^(1/2) + 25))/(10*(5 - 5^(1/2))^(1/2)))]

[Walter Roberson]

No that is symbolic. You need to double() that to get something numeric

[Ghazal Hnr]

I double it, I don't have error after unwrap it but it shows me a blank page

[Walter Roberson]

What shows up if you do

n_phase_1 = double(phase_1);
class(n_phase_1)
size(n_phase_1)
plot(n_phase_1)

[Ghazal Hnr]

thank youuuu, it works