# [gmx-users] error estimate

Sun Feb 5 15:19:20 CET 2012

```Dear Prof.

I computed the total radius gyration and the radius of gyration in x, y and z directions that all of them are into one file named gyrate.xvg. Then I want to calculate error estimate for all of them separately. I do as:

g_analyze -f gyrate.xvg -ee error.xvg
and is printed on terminal following context:

std. dev.    relative deviation of
standard       ---------   cumulants from those of
set      average       deviation      sqrt(n-1)   a Gaussian distribition
cum. 3   cum. 4
SS1   1.972797e+00   2.187285e-02   7.059432e-05       0.416    0.279
SS2   1.601256e+00   7.870806e-02   2.540292e-04       0.018   -0.152
SS3   1.614145e+00   7.842650e-02   2.531204e-04      -0.067   -0.161
SS4   1.611412e+00   7.958559e-02   2.568614e-04      -0.072   -0.177

Set   1:  err.est. 0.000596502  a 0.29217  tau1 24.8856  tau2 443.641
Warning: tau2 is longer than the length of the data (864000)
invalid fit:  e.e. 0.285911  a 0.995985  tau1 1434.16  tau2 1.41932e+09
Will fix tau2 at the total time: 864000
Set   2:  err.est. 0.00859257  a 0.995692  tau1 1432.7  tau2 864000
Set   3:  err.est. 0.00527967  a 0.588024  tau1 804.83  tau2 3603.55
a fitted parameter is negative
invalid fit:  e.e. 0.00421461  a 1.08722  tau1 1672.3  tau2 6955.25
Will fix tau2 at the total time: 864000
a fitted parameter is negative
invalid fit:  e.e. -nan  a 1.00449  tau1 1455.53  tau2 864000
Will use a single exponential fit for set 4
Set   4:  err.est. 0.00453113  a 1  tau1 1400.34  tau2 0

SS1,SS2,SS3 and SS4 are Rg, Rgx, Rgy and Rgz respectively, but I don't know about its remainder.

The error.xvg file has three columns, and has been written in the first lines of this file:
@ legend string 0 "av 1.972797"
@ legend string 1 "ee 0.000596502"

I averaged from this file as:
g_analyze -f error.xvg -av
and result was:
std. dev.    relative deviation of
standard       ---------   cumulants from those of
set      average       deviation      sqrt(n-1)   a Gaussian distribition
cum. 3   cum. 4
SS1   4.442130e-04   1.512862e-04   1.435945e-05      -0.412   -0.211
SS2   4.605313e-04   1.542594e-04   1.464166e-05      -0.566   -0.191

What is this? How can I find error estimate for all of radius of gyration, separately?