Retrieving numbers present within an array by knowing the coordinates

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);

Answer 1

[Stephen23]

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

Answer 2

[Torsten]

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))