Programming :: Simple Shell Script That Produce Digit Values

I just started learning shell programming and I'm trying to create a shell script that produce something like this:
Input: 1 234 5 678 9
Output: < <<< 5 >>> >
Input:abc d 1234 5 5 67890 e f ghij
Output:abc d <<<< 5 5 >>>< e f ghij
Characters with values less than 5 will display '<' digit values greater than 5 display '>'. The digit '5' will be left unchanged.

Below is my unfinished code:
#!/bin/sh
read userInput
for f in "$userInput"
do
f1="$(echo ${f} | sed "s/[^0-9]//g")"
if test $f1 -lt 4
then
f3='<'
elif test $f1 -gt 6
then
f3='>'
fi
f2="$(echo ${f} | tr "$f1" "$f3")"
echo $f2
done