IMPUTE2 missing filter option I went through the manuals and can't find the meaning of the below flag:

-filt_rules_l 'filter==0'


Here is the link to manual for this flag: filt_rules_l

Can anyone explain?

IMPUTE version: 

impute_v2.3.1_x86_64_dynamic




Edit: The full IMPUTE2 code is irrelevant, I am not using the command to impute, I received an imputed data and the script used to impute. This one flag was a mystery to me. I will update the post with impute software version when I find out.
I have never used this program, but reading the manual in the link it has to mean the following.

The manual says:


  Writing -filt_rules_l 'eur.maf&lt;0.05' on the command line would tell the program to remove any variants with eur.maf values less than 0.05 from the reference panel.


So, -filt_rules_l 'filter==0' would mean that the program removes any variants with filter values of 0 from the reference panel. In the legend file there should be a column named filter, which are filtered out when the value is 0.

Here is the example legend file, in your case there must be a custom additional column named "filter":

$ head ALL_1000G_phase1integrated_v3_chr1_impute.legend

id position a0 a1 afr.aaf amr.aaf asn.aaf eur.aaf afr.maf amr.maf asn.maf eur.maf
rs58108140 10583 G A 0.0407 0.1713 0.1311 0.2071 0.0407 0.1713 0.1311 0.2071
rs189107123 10611 C G 0.0142 0.0276 0.0140 0.0211 0.0142 0.0276 0.0140 0.0211