MATLAB: Subs don’t work properly

mathsubssymbolicSymbolic Math Toolbox

I'm try to replace a symbolic variable at my expression. Example at image below

I'm want to get x*0.375, but (3*x)/8 isn't equal. Maybe I'm doing something wrong?

Best Answer

syms  x a
expr=x*a
acounted=3/8
subs(expr,a,3/8)

3/8=0.3750,

Why do you think 3/8 and 0.3750 are not equal?

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MATLAB: Are symbolic expressions being rounded

Mathworks technical support have diagnosed the problem. Don't know what caused it originally but the 'FloatingPointOutput' setting in the symbolic preferences was set to 1.

Here is the solution to fix it:

>> sympref
ans = 
  struct with fields:
           FourierParameters: [1×2 sym]
           HeavisideAtOrigin: [1×1 sym]
            AbbreviateOutput: 1
               TypesetOutput: 1
         FloatingPointOutput: 1
      PolynomialDisplayStyle: 'default'
    MatrixWithSquareBrackets: 0
>> sympref('FloatingPointOutput','default');
>> double(sym('pi'))
ans =
   3.141592653589793
>> p = sym(pi);
>> piVpa = vpa(p)
 
piVpa =
 
3.1415926535897932384626433832795

MATLAB: Question about the summation of array of elements with complex double

sum(sym(m))

Best Answer

Related Solutions

MATLAB: Are symbolic expressions being rounded

MATLAB: Question about the summation of array of elements with complex double

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