vpasolve only shows 5 significant figures

Hello,

MATLAB help shows the following command should produce the result shown below

syms x
S = vpasolve(sin(x) == 1/2, x)

S = 

0.52359877559829887307710723054658

but on my machine it produces the following result

S = 0.5236

Similarly the command below should produce the result shown below

vpa(pi,10)

ans = 

3.141592654

but on my machine it produces the following result

ans = 3.1416

Why am I only getting 4 decimal places of precision? I've tried the digits(10) command but it doesn't help.

Any help greatly appreciated.

Thanks!

Answer 1

[Steven Lord]

Let's make sure you're using the functions from Symbolic Math Toolbox. What do these commands display?

which -all syms

/MATLAB/toolbox/symbolic/symbolic/syms.m

which -all vpasolve

/MATLAB/toolbox/symbolic/symbolic/@sym/vpasolve.m  % sym method

which -all vpa

/MATLAB/toolbox/symbolic/symbolic/vpa.m
/MATLAB/toolbox/symbolic/symbolic/@sym/vpa.m  % sym method

Also what are your symbolic preferences? In particular, what is the FloatingPointOutput preference value?

sympref

ans = struct with fields:
           FourierParameters: [1    -1]
           HeavisideAtOrigin: 1/2
            AbbreviateOutput: 1
               TypesetOutput: 1
         FloatingPointOutput: 0
      PolynomialDisplayStyle: 'default'
    MatrixWithSquareBrackets: 0

[Eddie]

Hello Steven!

I get the following output:

>> which -all syms
\MATLAB\R2023a\toolbox\symbolic\symbolic\syms.m
>> which -all vpasolve
\MATLAB\R2023a\toolbox\symbolic\symbolic\@sym\vpasolve.m  % sym method
>> which -all vpa
\MATLAB\R2023a\toolbox\symbolic\symbolic\vpa.m
\MATLAB\R2023a\toolbox\symbolic\symbolic\@sym\vpa.m  % sym method
>> sympref
ans = 

  struct with fields:

           FourierParameters: [1    -1]
           HeavisideAtOrigin: 0.5000
            AbbreviateOutput: 1
               TypesetOutput: 1
         FloatingPointOutput: 1
      PolynomialDisplayStyle: 'default'
    MatrixWithSquareBrackets: 0

I was able to change the FloatingPointOutput to 0 using

    sympref('FloatingPointOutput',0)

and it seems to have fixed my issue! Not sure why it woudln't have been defaulted that way or how I would have changed it but I have it working now. thanks!!

[Walter Roberson]

Heh. I knew the cause of the problem from the Title to the question alone ;-)

[Eddie]

Haha, Google Gemini needs to scrape your brain then because it didn't ;)

Thanks guys!