subs command gives symbolic output instead of integers

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Akkineni 2014-3-11

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https://ww2.mathworks.cn/matlabcentral/answers/121112-subs-command-gives-symbolic-output-instead-of-integers

回答： Walter Roberson 2014-3-11

I observe 'subs' command in Matlab 2013b and 2014a gives output in a symbolic fassion. I have to use 'double' command to convert into numbers. Where as in previous versions.

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Answer 1

Walter Roberson 2014-3-11

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I do not have the toolbox to test with, but symbolic numbers is what I would expect, due to the potential for loss of precision if double() is always output. For example,

subs(sym('2^N'), 'N', 55)

I would expect to give the exact integer result rather than converting it to double (which would only have 53 bits precision rather than e.g., 55)

Even something like,

subs(sym('PI/2'), 'PI', sym('pi'))

I would certainly expect to give Pi/2 as symbolic form, not the double precision approximation.