Matlab doesn't evaluate derivative of Riemann zeta function

Hello everyone,

I'm pretty new to Matlab, so please excuse if this is a stupid question.

Yesterday I wrote the following with which I successfully evaluated both the zeta function and its derivative and arrived at a numerical value for c:

syms x 
g=zeta(x)
a=subs(g,x,0.49935)
gp=diff(g,x)
b=subs(gp,x,0.49935)
c=b/a

Today, however, I don't know why, typing the same thing I get

g =
zeta(x)

a =
   -1.4578

gp =
zeta(1, x)

b =
zeta(1, 9987/20000)

c =
-(1125899906842624*zeta(1, 9987/20000))/1641346078514575,

i.e., id doesn't evaluate the derivative anymore.

I tried it in a different way, too, typing

>> f=sym('zeta(x)');

>> dfdx=diff(f)

dfdx =

zeta(1, x)

>> x=.5;

>> eval(dfdx)

And this is the error I got:

??? Error using ==> zeta
Too many input arguments.

Error in ==> sym.eval at 15
    s = evalin('caller',vectorize(map2mat(char(x))));>> f=sym('zeta(x)');

What am I doing wrong? And why did it work yesterday and not today? I would be extremely thankful for any kind of help or support.

Anna

Answer 1

[Anna Klabunde]

I deinstalled Matlab and installed it again. Now it works again. No idea why. Output: g =

zeta(x)

a =

   -1.4578

gp =

zeta(1, x)

b =

   -3.9123

c =

    2.6837

Anyone had a similar problem, just out of curiosity? Could you solve it without deinstalling and re-installing Matlab?

Cheers, Anna

[Walter Roberson]

which -all zeta

might have shown that you had accidentally created a new zeta.m file.