How can I plot this function such as all values of |f(1/z)| be more clear and how can I plot the cosine of the phase of this function ?

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Aisha Mohamed 2022-7-8

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https://ww2.mathworks.cn/matlabcentral/answers/1755960-how-can-i-plot-this-function-such-as-all-values-of-f-1-z-be-more-clear-and-how-can-i-plot-the-c

评论： Aisha Mohamed 2022-8-17

采纳的回答： Benjamin Kraus

When I plot this function (thanks for every help).

f(1/z) = (0.1000 -0.3000i)z^-1 + (0.2121-0.0008i)z^-2 + (-0.9000-0.0010i)z^-3

I want to study time evolution of this functions, but I have got from its figure that:

1-the |f(1/z)| seems to take zero every where exept at z=o when it goes to infiniy, even when I tried to change the values of z , I always get the same graph

My questions are:

1:How can I plot this figure such that all values of z in the plane appeare more clear to enable me to study its movement over time?

2- How can I plot the cos for the phase of f(1/z) to get more cleare plotting of the phase of this function?

p1=[(0.9000+0.0010i) (0.2121-0.0008i) (0.1000 -0.3000i)];

This is the figure of |f(1/z)| and the phase of f(1/z)

I used this link:

re_z = -6.005:.01:6.005;

im_z= -6.005:.01:6.005;

[re_z,im_z] = meshgrid(re_z,im_z);

z = re_z + 1i*im_z;

xlabel('x')

ylabel('y')

f_of_1_over_z_result = polyval(p1,1./z);

figure();

subplot(2,2,3)

surf(re_z,im_z,abs(f_of_1_over_z_result),'EdgeColor','none')

colorbar

title('|f(1/z)|')

xlabel('Z_R')

ylabel('Z_I')

subplot(2,2,4)

surf(re_z,im_z,angle(f_of_1_over_z_result),'EdgeColor','none')

colorbar

title('phase of f(1/z)')

xlabel('Z_R')

ylabel('Z_I')

grid on

I appriciate any help.

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采纳的回答

Benjamin Kraus 2022-7-8

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https://ww2.mathworks.cn/matlabcentral/answers/1755960-how-can-i-plot-this-function-such-as-all-values-of-f-1-z-be-more-clear-and-how-can-i-plot-the-c#answer_1003145

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It looks like the nearly infinite value in your data is drowning out the remaining data. You can fix this by changing the z-limits and color limits, using the zlim and caxis commands.

For example:

% Prepare the data for plotting

p1=[(0.9000+0.0010i) (0.2121-0.0008i) (0.1000 -0.3000i)];

re_z = -6.005:.01:6.005;

im_z= -6.005:.01:6.005;

[re_z,im_z] = meshgrid(re_z,im_z);

z = re_z + 1i*im_z;

f_of_1_over_z_result = polyval(p1,1./z);

% Create first picture

nexttile

surf(re_z,im_z,abs(f_of_1_over_z_result),'EdgeColor','none')

colorbar