[R] Warning message help

[Guenther, Cameron]

I am trying to great a new column of effort data from an existing vector
of gears used.
It is a simple code where 

effort[Gear==300]=(DIST_TOW*7412)
effort[Gear==301]=(DIST_TOW*7412)

The code appears to work for some of the data but fails for others and
inserts a NA value

I also get this warning message

Warning message:
number of items to replace is not a multiple of replacement length 

Can anybody tell me what this means.
thanks

Cameron Guenther 
Associate Research Scientist
FWC/FWRI, Marine Fisheries Research
100 8th Avenue S.E.
St. Petersburg, FL 33701
(727)896-8626 Ext. 4305
cameron.guenther at myfwc.com