What is a(:,2:3)?
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a = [ 1 2 3 4 5; 2 3 4 5 6; 3 4 5 6 7; 4 5 6 7 8]
3 个评论
Azzi Abdelmalek
2016-5-17
What space?
Bella
2016-5-17
Kelvin
2023-2-7
1 2 3 4 5 2 3 4 5 6 3 4 5 6 7 4 5 6 7 7 It’s a matrix
采纳的回答
Todd Leonhardt
2016-5-17
编辑：Todd Leonhardt
2016-5-17
1 个投票
a(:,2:3) is saying "give me the submatrix of a which consists of all rows and the 2nd and 3rd columns".
If you don't have MATLAB you can get a free evaluation, at least for academic purposes. You can also do many of the things MATLAB can do using open-source Octave (though there are significant limitations). Get one of those and then try to do this stuff yourself so you actually learn something ;-)
4 个评论
Bella
2016-5-17
Todd Leonhardt
2016-5-17
编辑：Todd Leonhardt
2016-5-17
Then I believe you entered something wrong. It should be [2 3; 3 4; 4 5; 5 6].
Bella
2016-5-17
Image Analyst
2016-5-17
What do you mean "it said it was wrong"? +*What*_ said that? MATLAB? If so, post the error message here. If you got that you must have left off the top row and done this:
a = [
2 3 4 5 6;
3 4 5 6 7;
4 5 6 7 8]
a(:,2:3)
However there is nothing in MATLAB that says anything is wrong about that - no error message or anything.
更多回答（2 个）
Greg Biyu
2019-3-12
0 个投票
what is (:,:,3)?
5 个评论
Steven Lord
2019-3-12
Ghislain Rutayisire
2021-2-22
exactly what i was looking for!
Anu Sebastian
2021-3-9
What you mean by G=he(:,:,2); Especially (:,:,2)
Walter Roberson
2021-3-10
You were dealing with
he = imread('1.jpg');
which reads the image file and stores the result as an array.
If 1.jpg had been a color image, then the resulting array he would have been a 3D array, with the first index being for rows (vertical height), and the second index being for columns (horizontal distance), and for the third index being for color panes. The first color pane for an RGB image holds the Red component. The second color pane for an RGB image holds the Green component. The third color pane for an RGB image holds the Blue component.
Thus, if 1.jpg had been an RGB image, then he(:,:,2) would be a 2D array containing just the green component of the color information for each pixel.
However, your 1.jpg was not an RGB image; it was a grayscale image, and there is no red or green or blue component. If you needed specifically the green information (for example you were examining leaves) then you would not be able to proceed using that image. If, though, the green component was being used to approximate brightness (eyes are more sensitive to green), then you could just use the data you received instead. For example,
if ndims(he) > 2
G = he(:,:,2);
else
G = he;
end
end
Anu Sebastian
2021-3-10
Thank you sir
Maria Celeste
2022-11-2
0 个投票
What are the answers to these? >> B(2:5) 20. >> A(4:8) 21. >> A(:,3) 22. >> B(:,3:4) 23. >> A(2:3,:) 24. >> B(2:3, 2:4) 25. >> length (A)
1 个评论
Walter Roberson
2022-11-2
B(2:5) is 'TAIF'
A(4:8) is [81 84 83 72 76]
A(:,3) is [84; 83]
B(:,3:4) is ['II'; 'XN'; 'YX']
A(2:3,:) is an error because A does not have 3 or more rows.
B(2:3, 2:4) is ['FXN'; 'KYX']
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