Retrieving numbers present within an array by knowing the coordinates

Question

Alberto Acri 2023-2-14

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1912410-retrieving-numbers-present-within-an-array-by-knowing-the-coordinates

编辑： Stephen23 2023-2-14

Hi! I have a fairly easy question but whose error I can't figure out.

I have the array "image_DEF_number_pixel" and the coordinates (x,y) in "union". I would like to create a vector containing the values present in "image_DEF_number_pixels" based on the coordinate (x,y) present in "union".

For example:

--> line 129 of "union" has coordinates (202, 188)

--> the value I want to get in a new vector is 186 because at coordinate (202, 188) inside "image_DEF_number_pixel" there is number 186.

Here is the line of code I am using:

image_DEF_numero_pixel = importdata('image_DEF_numero_pixel.mat');
union = importdata('union.mat');
vector = image_DEF_numero_pixel(union);

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Answer 1

Stephen23 2023-2-14

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https://ww2.mathworks.cn/matlabcentral/answers/1912410-retrieving-numbers-present-within-an-array-by-knowing-the-coordinates#answer_1171350

编辑：Stephen23 2023-2-14

在 MATLAB Online 中打开

The simple and efficient MATLAB approach is to use SUB2IND:

SI = load('image_DEF_numero_pixel.mat')
SI = struct with fields:
    image_DEF_numero_pixel: [512×512 double]
im = SI.image_DEF_numero_pixel;
SU = load('union.mat')
SU = struct with fields:
    union: [946×2 double]
un = SU.union;
idx = sub2ind(size(im),un(:,1),un(:,2));
out = im(idx)
out = 946×1
   188
   194
   182
   199
   198
   198
   191
   192
   191
   178

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Answer 2

Torsten 2023-2-14

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1912410-retrieving-numbers-present-within-an-array-by-knowing-the-coordinates#answer_1171355

在 MATLAB Online 中打开

image_DEF_numero_pixel = importdata('image_DEF_numero_pixel.mat')
union = importdata('union.mat')
vector = arrayfun(@(x,y)image_DEF_numero_pixel(x,y),union(1:size(union,1),1),union(1:size(union,1),2))