Syntax:

$ ./vartools -i EXAMPLES/4 -ascii -oneline \
    -chi2 \
    -changeerror \
    -chi2

Name                = EXAMPLES/4
Chi2_0              =      5.19874
Weighted_Mean_Mag_0 =  10.35137
Mean_Mag_1          =  10.35142
RMS_1               =   0.00209
Npoints_1           =  3227
Chi2_2              =      1.00031
Weighted_Mean_Mag_2 =  10.35142

Calculate the chi^2 per degree of freedom of the light curve EXAMPLES/4. In between the two calls to -chi2 were replace the formal errors in the light curve with the RMS of the light curve. As a result, the second call to -chi2 yields chi^2 per degree of freedom very close to 1.0