does 'VPA' changes the type of a data variable ?

Hi everyone

I have a question about the data type.

I know that all data are double floating-point in Matlab by default.

I've written this code and when I use 'whos function' for 'z', Matlab says that z is 'double' which is what I expect.

s=500;
t=[12 25 36 12 1 8 9 20 9 7 5 2 74];
z=0;
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
for i=1:10
z=z+t(i);
end
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
z=s-z;

whos function:

whos z
  Name      Size            Bytes  Class     Attributes

  z         1x1                 8  double              

I've added one line (line 8) and used VPA, when I repeat what I've said above, Matlab says that z is 'syms'.

s=500;
t=[12 25 36 12 1 8 9 20 9 7 5 2 74];
z=0;
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
for i=1:10
z=z+t(i);
end
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
z=vpa(z,10);
z=s-z;

whos function:

whos z
  Name      Size            Bytes  Class    Attributes

  z         1x1               112  sym                

does VPA change the data type?

I really appreciate any explanation for this change and totally about syms.

Answer 1

[Chunru]

vpa(x) uses variable-precision floating-point arithmetic (VPA) to evaluate each element of the symbolic input x.

The input to x is supposed to be symbolic.

syms x
p = sym(pi);
piVpa = vpa(p)

piVpa = 

3.1415926535897932384626433832795

class(p)  % The type is sym

ans = 'sym'

a = sym(1/3);
f = a*sin(2*p*x);
fVpa = vpa(f)

fVpa =