[SOLVED] Replacement according to an index

[TideMan]

Here is a rather ugly piece of script that replaces HH in a string with a value that depends on an index, then executes the resulting string. Is there a more elegant way to do it? In Matlab, I'd have a cell array HH={'00','06','12','18'}; which I can address using HH{$imx}. Is such a thing possible in a bash script?

# Depending upon imx, replace HH by the appropriate hour value
if [ $imx = 1 ]
then
	${str/HH/00}
elif [ $imx = 2 ]
then
	${str/HH/06}
elif [ $imx = 3 ]
then
	${str/HH/12}
elif [ $imx = 4 ]
then
	${str/HH/18}
else
	echo $imx '  is outside the range'
fi

[TideMan]

Problem solved. I missed the chapter on arrays in the text book

HH=(00 06 12 18)
${str/HH/${HH[$imx]}}