Is there any way to convert variables from list to arrays?

Question

Abhay SAMUDRASOK 2018-4-24

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评论： Stephen23 2018-4-24

I have 2 arrays

a = [1 2 3]
b = [2 3 4]

and a list

c = {'a', 'b'}

when I use cell2mat(c(1,1)), I get a, but what I want is [1 2 3]. Is there any way to achieve it?

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Stephen23 2018-4-24

"I have ... a list"

MATLAB does not have a "list" data type. What you show is called a cell array:

https://www.mathworks.com/help/matlab/cell-arrays.html

https://www.mathworks.com/help/matlab/data-types_data-types.html

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Answer 1

Stephen23 2018-4-24

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编辑：Stephen23 2018-4-24

在 MATLAB Online 中打开

Simply store the data in one structure, and then it is trivially easy (no slow, buggy eval is required):

>> S.a = [1,2,3];
>> S.b = [2,3,4];
>> C = {'a','b'};
>> S.(C{1})
ans =
   1   2   3

Simpler code through better code design: faster, neater, simpler, more efficient, easiest to debug, less complex. Why waste your time learning bad ways to write code?:

https://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval

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Answer 2

Fangjun Jiang 2018-4-24

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https://ww2.mathworks.cn/matlabcentral/answers/397120-is-there-any-way-to-convert-variables-from-list-to-arrays#answer_316950

编辑：Fangjun Jiang 2018-4-24

在 MATLAB Online 中打开

a=1:3;
b=2:4;
c={'a','b'};

you could do

d=eval(c{1})

or, you should do

clear c;
c.a=a;
c.b=b;
MyVar='a';
c.(MyVar)

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Stephen23 2018-4-24

编辑：Stephen23 2018-4-24

Do NOT use eval for trivial code like this. The MATLAB documentation specifically recommends against doing what this answer shows: "A frequent use of the eval function is to create sets of variables such as A1, A2, ..., An, but this approach does not use the array processing power of MATLAB and is not recommended. The preferred method is to store related data in a single array."

Source: https://www.mathworks.com/help/matlab/matlab_prog/string-evaluation.html

Using eval is how beginners force themselves into writing slow, complex, buggy code that is hard to debug. Read more here:

https://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval

See my answer for a simple solution that avoids these problems entirely.

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