SIGFILTER
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The usage of sigfilter is (as it should be) trivial for users of XtalView software. Unlike resfilter, no space group information is required (see below):

sigfilter mydata.fin cutoff > outdata.fin

Where cutoff is the sigma cutoff to be applied to the data.

There are three different methods of specify the columns to be examined for the intensity and the sigma value. They are as follows:

1. sigfilter mydata.fin cutoff. This command assumes that column 4 is the information (the "next" column after the h, k, l information) and that column 5 is the sigma value. This is likely to be the most common usage of the program.

2. sigfilter mydata.fin cutoff numpair. This command indicates that the "numpair" pair of columns after the h, k, l is a "paired" set of values and sigmas to be considered for rejection. E.g. sigfilter mydata.fin 3.0 2 will apply a sigma cutoff of 3.0 to columns six and seven of the file (h, k, l, value1, sigma1, VALUE2, SIGMA2). Similarly method #1 can be repeated with the command sigfile mydata.fin 3.0 1

3. sigfilter mydata.fin cutoff col1 col2. This command indicates that col1 is the value column and col2 is the sigma column. These columns the number of columns after the h, k, and l columns so sigfilter mydata.fin 3.0 1 2 repeats method #1 and sigfilter mydata.fin 3.0 3 4 is the same as sigfilter mydata.fin 3.0 2. Note that this form of the command should handle fairly difficult cases.

Following the UNIX philosophy, the reflections outputted by the program go to the stdout so they can be written to a file or piped into other UNIX routines such as sort or awk or grep. The program can also accept files from stdin if the file is specified as "-". For example:

sort -n mydata.fin | sigfilter - 20.0 4.0 > outdata.fin

Perhaps most importantly, sigfilter is designed to work in parallel with other steps of sigfilter and resfiltering. Thus to restrict the data of a file where the sigma of the first two columns and second two columns of data are greater than 3.0 in the resolution of 20.0 to 4.0, we would write:

resfilter mydata.fin 20 4 | sigfilter - 3.0 1 | sigfilter - 3.0 2 > outdata.fin

The log of the step is reported to the stderr so it can be examined for errors. For example:

SIGFILTER ******************************************************
                                          v 1.0   C. Putnam 1997


sigfilter> A sigma cutoff of 3 will be applied to the data.

sigfilter> Opened file tma308_pt2.sca.

sigfilter> Accepted 30593 reflections.
sigfilter> Rejected 17066 reflections below sigma cutoff.
sigfilter> Rejected 2 reflections with incomplete lines.


****************************************************** SIGFILTER

XtalView reflection files (*.fin, *.df, *.phs) are "unformatted". Space-deliminated columns contain h,k,l and 4-8 columns of values. .fin files are of the format H K L F1 SIGF1 F2 SIGF2 (unmeasured are marked with F=0.00 and SIGF=9999.00). .df, double-fin, are of the format H K L F1 SIGF1 F2 SIGF2 F3 SIGF3 F4 SIGF4. .phs files have the columns H K L FO FC PHS or H K L FO FOM PHS. For example, the following is a exerpt of a .fin file:

   0   0   8  1084.88    50.04     0.00  9999.00
   0   0  12  2850.27   121.67     0.00  9999.00
   0   0  14  1675.91    67.00     0.00  9999.00

A Final Word

Praise and requests for options that would be useful are also welcome.