[gmx-users] g_analyze negative

[Jacob Spooner]

Hello gmx-users,

I am attempting to use g_analyze to find the error estimate on the average volume of my system.  Using an .xvg file with my volume data and the -ee flag I receive the following message.  

Found only 1 number on line, assuming no time is present.
Read 1 sets of 611700 points, dt = 1

                                                                                           relative deviation of
                                standard                  std. dev.           ---------   cumulants from those of
set      average       deviation                  sqrt(n-1)             a Gaussian distribition
                                                                                           cum. 3   cum. 4
SS1   1.480894e+01   1.283016e-01   1.640450e-04       0.070    0.005

a fitted parameter is negative
invalid fit:  e.e. 0.00023263  a 1.01491  tau1 1.33511  tau2 23.436
Will fix tau2 at the total time: 611699
a fitted parameter is negative
invalid fit:  e.e. nan  a 1.00002  tau1 1.24851  tau2 611699
Will use a single exponential fit for set 1
Set   1:  err.est. 0.000259141  a 1  tau1 1.24772  tau2 0

can anybody suggest to me what would be causing this trouble in fitting? does this indicate a problem with my data?

Thank you in advance

Jake Spooner