Dimensions of arrays being concatenated are not consistent

Question

Awais Khan 2020-2-12

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/505004-dimensions-of-arrays-being-concatenated-are-not-consistent

评论： Walter Roberson 2020-2-12

Hi community, i am doing a task, of extracting color features and gobar features, after extracting these features, i am trying to cancate them but it gives error message

Error using horzcat

Dimensions of arrays being concatenated are not consistent.

Error in practice_code (line 19)

Fused_Features = [Extracted_Color_Features, Extracted_Gabor_Features];

i am trying to use vertcat and horzcat function for cancatenating these two features the reason of using these two function is because color features obtained in horizontal position, and gobar features are obtained in vertical features. but still same error are shown. the dimension of color features are 4478x1 and gobar features are 24000x1

so what can i do?

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Answer 1

Walter Roberson 2020-2-12

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https://ww2.mathworks.cn/matlabcentral/answers/505004-dimensions-of-arrays-being-concatenated-are-not-consistent#answer_415131

在 MATLAB Online 中打开

Fused_Features = [Extracted_Color_Features; Extracted_Gabor_Features];

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Awais Khan 2020-2-12

can you explain what is the purpose of ; because i am using same code but instead of ; i am using , as a result it given an error.

Walter Roberson 2020-2-12

在 MATLAB Online 中打开

https://www.mathworks.com/help/matlab/ref/vertcat.html

vertcat is equivalent to using square brackets for vertically concatenating arrays. For example, [A; B] is equal to vertcat(A,B) when A and B are compatible arrays.

https://www.mathworks.com/help/matlab/ref/horzcat.html

horzcat is equivalent to using square brackets for horizontally concatenating arrays. For example, [A,B] or [A B] is equal to horzcat(A,B) when A and B are compatible arrays.

Phrasing that another way:

When you write [A, B] or [A B], what really gets called is horzcat(A,B) -- writing [] is "syntactic sugar", something to make programming easier but which is internally translated to something else.
When you write [A;B], what really gets called is vertcat(A,B) -- more syntactic sugar

Also, when you code

[A
 B]

what really gets called is vertcat(A,B). And

[A B
 C D]

would internally be translated to

vertcat(horzcat(A, B), horzcat(C, D))

If you happened to have

[A B
 C]

then you should suspect that there is an error, but it is not necessarily an error. The important part is not the number of expressions: it is whether the expressions expand to compatible sizes. It is, for example, completely valid to have