How to keep more digits when use symbolic expressions

my codes is simple,

syms x
f(x)=0.123456789*x

f(x) = 

f(1)

ans = 

sympref('FloatingPointOutput', true);
f(x)=0.123456789*x

f(x) = 

f(1)

ans = 

0.1235

When use sympref, it will only keep four digits, (I want to show 0.123456789). Is there any way to keep them all.

Answer 1

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From the documentation on 'FloatingPointOutput' —

• The true value option displays symbolic results in the short fixed-decimal format with 4 digits after the decimal point.

To get more digits, use the digits function and the vpa function, together or separately —

syms x
f(x)=0.123456789*x

f(x) = 

f(x)=0.123456789*x

f(x) = 

F = vpa(f,64)                                               % Specify 64 Digits In The 'vpa' Output

F(x) = 

.