How to derive a variable name from a variable?

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Rightia Rollmann
Rightia Rollmann 2017-2-7
编辑： Jan 2017-2-8
How to derive a variable name from a variable?
A = [5 6 7 8];
B = ‘A’;
A(1) % this works and return the first element of A which is 5
B(1) % this doesn’t work like the code above
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Rightia Rollmann
Rightia Rollmann 2017-2-7
What I want to do is to access the first column and then the second column of a 5-by-7 matrix which is the value of a field named B. B is the third field of struct A. How can I do it dynamically best?
Adam
Adam 2017-2-8
If B is a field of A why are you trying to create a variable B that represents the whole of A.
Just A.( 'B' ) would give what you want. Fields are not really ordered in a struct, at least not for general usage.

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采纳的回答

Stephen23
Stephen23 2017-2-7
编辑：Stephen23 2017-2-7
Although often loved by beginners, dynamically accessing variable names is not a robust, fast, or good way to write code. It makes code hard to read, slow, difficult to debug, and has other disadvantages too:
https://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval
If you really need to access the names dynamically, then consider using a structure: it is fast and easy to access structure field names dynamically:
S.A = [5,6,7,8];
x = 'A';
S.(x)
https://www.mathworks.com/help/matlab/matlab_prog/generate-field-names-from-variables.html

更多回答（2 个）

Star Strider
Star Strider 2017-2-7
MATLAB does not recognise char(0145) and char(0146) as quotation marks in code.
A = [5 6 7 8];
B = 'A' % Sets ‘B’ TO Be Character ‘A’
B = A
B(1)
produces:
B =
A
B =
5 6 7 8
ans =
5
Jan
Jan 2017-2-8
编辑：Jan 2017-2-8
According to your comment, which is another problem than the original question:
A.B(:, 1:2)

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