MRTG Error : WARNING: Problem with Externale get ‘/etc/mrtg/system swap’: Expected a Number for ‘out’ but got ”

How to solve this problem ?

WARNING: Problem with Externale get '/etc/mrtg/system swap':
Expected a Number for 'out' but got ''

Do:

#pico /etc/mrtg/system

And replace all your SWAP code with this one:

if [ "$TYPE" = "swap" ]; then
INDATA=`/usr/bin/free -b | grep "Swap:" | sed 's/ * / /g' | cut -d ' ' -f2`
OUTDATA=`/usr/bin/free -b | grep "Swap:" | sed 's/ * / /g' | cut -d ' ' -f3`