Am I creating dynamic variable names?

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hmhuang
hmhuang 2021-11-20
评论： hmhuang 2021-11-22
Recently I came across a popular thread in MATLAB Answers: https://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval#answer_236124
After reading this thread, I am still not sure I have created "dynamic variable names", which should be avoided as suggested in that thread.
I have a code snippet as following:
data = [1, 2, 3];
centerX = data(1);
centerY = data(2);
centerZ = data(3);
% And use these variables afterwards
Should I avoid creating those (probably dynamic) variable names, i.e., centerX, centerY, centerZ to use those data and simply/directly use data(1), data(2), data(3) instead?
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hmhuang
hmhuang 2021-11-21
@Stephen Because of the examples given in https://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval#answer_236124:
  • matrix1, matrix2, matrix3, matrix4, ...
  • test_20kmh, test_50kmh, test_80kmh, ...
  • nameA, nameB, nameC, nameD, ...
hmhuang
hmhuang 2021-11-21
编辑：hmhuang 2021-11-21
@Stephen But now I understand those example given in that thread were dynamically created using eval, which is different from my hardcoded ones.

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回答（1 个）

Sulaymon Eshkabilov
Sulaymon Eshkabilov 2021-11-20
What you are doing here is not dynamic variable naming. You're assigning a new variable name from your already assigned data.
This example shows the dynamic variable naming and assigning values to the dynamically named variables (U and V):
for jj=1:5
eval(['V' num2str(jj) '= jj'])
eval(['U' num2str(jj) '= ' 'V' num2str(jj) '*jj'])
end
Which is NOT recommended to employ.
That is equivalent to:
V = 1:5;
U = V.*V;
This one is the recommended one.
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Image Analyst
Image Analyst 2021-11-22
@hmhuang, no. He did not create the dynamically named variable. His variable names are hard coded. If the file was called foo.png, there is no variable created called foo. You could do that with eval() but as we've been discussing, that's not recommended so that's why he probably did not show it. However he's saying that some people think they want to do it because they don't realize the problems it can cause.

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