AUTORG

AUTORG, is a command-line program to estimate the radius of gyration (R_g) using the well known Guinier approximation

I(s) = I(0)exp(-s²R_g²/3).

The value of R_g is estimated from the best possible linear fit of ln[I(s)] versus s² (a Guinier plot), which is valid for sufficiently small scattering vectors (in the range up to sR_g ≤ 1.3). The radius of gyration value provides an estimate of the overall size of a particle (the root mean square distance to center-of-mass in a particle). Moreover, linearity of the Guinier plot is a sensitive indicator of the quality of the experimental data, and deviations from linearity usually point to strong interference effects, polydispersity of the samples or improper background subtraction. Based on that the program also estimates the quality of the input data. Please refer to the paper cited above for further details about the implemented algorithm.

 

autorg [OPTIONS] <DATAFILE(S)>

 

 

Short option	Long option	Description
-o	--output <FILE>	Relative or absolute path to save result. If the output file name has ".csv" extension the output will be in comma separated values (CSV) format unless format is specified (see next option).
-f	--format <FORMAT>	Output format, one of: csv, ssv, table. 'csv' will force to produce the output in Excel-compatible comma separated values format, a header will be written. 'ssv' will force to produce the output in machine-readable space separated format without a header; the sequence of values is same as in CSV format apart from the file name - it will be written last, not first. 'table' will force to produce the output as a human-readable table with round values. This is the default value if more than one input file is given.
	--mininterval <NUMBER>	Minimum acceptable Guinier interval length in points. Default is '10'.
	--smaxrg <NUMBER>	Maximum acceptable smaxRg value. Default is '1.3'.
	--sminrg <NUMBER>	Maximum acceptable sminRg value. Default is '1.0'.
-v	--version	Print version information and exit.
-h	--help	Print a summary of arguments and options and exit.

 

autorg input files

AUTORG uses the SAS experimental data files (*.dat) in ASCII format containing 3 columns: (1) momentum transfer, (2) experimental intensity and (3) experimental errors. If errors are not present, they are estimated as 4% of the intensity.

autorg output

AUTORG does not produce any output files unless the output option was specified.

AUTORG output includes:

Field	Description
File	DATAFILE name.
Rg	Estimated radius of gyration (Rg). If the input data was in Å-1 the unit of Rg is Å; if the input data was in nm-1 the unit of Rg is nm.
Rg StDev	Standard deviation of the Rg value. The accuracy of Rg is estimated by taking into account not only the error propagation in the selected fit as usual but also by accounting for the deviation of Rg values calculated from other consistent intervals, accounting to some extent for systematic errors in the Rg determination.
I(0)	Extrapolated scattering intensity at zero angle I(0) (forward scattering).
I(0) StDev	Standard deviation of the I(0) value. Please note that this value is currently estimated only from the selected interval and therefore is underestimated.
First point	First point of the Guinier interval. Counting of data points starts from 1. Data points before the first point should not be used in further data processing.
Last point	Last point of the Guinier interval. In table format total number of points is given in brackets.
Quality	Estimated data quality. 1.0 - means ideal quality, 0.0 - unusable data. In table format it is given in percent (100% - ideal quality, 0% - unusable data). Please note that this estimation is based only on the Guinier interval (very low angles).
Aggregated	If aggregation was detected from the slope of the data curve at low angles the value is '1', otherwise '0'.