How can i extract the values in complex double array

Question

feras 2023-8-30

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2014911-how-can-i-extract-the-values-in-complex-double-array

评论： Mathieu NOE 2023-8-30

I have the below complex double array, when i want to extract the fourth value and the ones which are above of the fourth one (like H(5) H(6) H(7) ....) Matlab says " All zero sparse: 1×1". so How can i extract them ?

H=

(1,1) -0.0181 - 0.0365i

(2,1) 0.2017 - 0.0552i

(3,1) 0.0795 - 0.0786i

(2,2) -0.0173 - 0.0370i

(3,2) 0.2023 - 0.0551i

(4,2) 0.0794 - 0.0785i

(3,3) -0.0166 - 0.0374i

(4,3) 0.2028 - 0.0551i

(5,3) 0.0793 - 0.0785i

(4,4) -0.0158 - 0.0378i

(5,4) 0.2034 - 0.0550i

(6,4) 0.0793 - 0.0784i

(5,5) -0.0151 - 0.0383i

(6,5) 0.2040 - 0.0549i

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James Tursa 2023-8-30

Do you mean extract the fourth non-zero value? In memory order? Please post an example input and exact output you want.

Mathieu NOE 2023-8-30

在 MATLAB Online 中打开

hello

according to your post H would be a 2D and not 1D arry so when you say the fourth and above index is fine for a 1D array but I don't know what you need to extract for a 2D array

H(1,1) = -0.0181 - 0.0365i;

H(2,1) = 0.2017 - 0.0552i;

H(3,1) = 0.0795 - 0.0786i;

H(2,2) = -0.0173 - 0.0370i;

H(3,2) = 0.2023 - 0.0551i;

H(4,2) = 0.0794 - 0.0785i;

H(3,3) = -0.0166 - 0.0374i;

H(4,3) = 0.2028 - 0.0551i;

H(5,3) = 0.0793 - 0.0785i;

H(4,4) = -0.0158 - 0.0378i;

H(5,4) = 0.2034 - 0.0550i;

H(6,4) = 0.0793 - 0.0784i;

H(5,5) = -0.0151 - 0.0383i;

H(6,5) = 0.2040 - 0.0549i;

imagesc(abs(H));colorbar('vert')

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Answer 1

MYBLOG 2023-8-30

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2014911-how-can-i-extract-the-values-in-complex-double-array#answer_1297406

在 MATLAB Online 中打开

You can achieve this using logical indexing and comparison of the magnitudes of the complex values. Here's how you can extract the fourth value and the values above it in MATLAB:

% Given complex array H
H = [
    -0.0181 - 0.0365i
     0.2017 - 0.0552i
     0.0795 - 0.0786i
    -0.0173 - 0.0370i
     0.2023 - 0.0551i
     0.0794 - 0.0785i
    -0.0166 - 0.0374i
     0.2028 - 0.0551i
     0.0793 - 0.0785i
    -0.0158 - 0.0378i
     0.2034 - 0.0550i
     0.0793 - 0.0784i
    -0.0151 - 0.0383i
     0.2040 - 0.0549i
];
% Extract the fourth value
fourth_value = H(4);
% Find the indices of values above the fourth value
above_fourth_indices = abs(H) > abs(fourth_value);
% Extract the values above the fourth value
values_above_fourth = H(above_fourth_indices);
% Display the results
disp('Fourth Value:');
disp(fourth_value);
disp('Values Above Fourth Value:');
disp(values_above_fourth);