How to create greek letter with superscript and subscript in LEGEND OF PLOT

My goal is to create a legend entry which displays sigma_(D)^(2) ft/sec^(2)

That is, the greek letter sigma has a subscript of 'D' and a superscript of '2' and units of "ft/sec^(2)"

I coded this in my legend entry, and, upon doing so, I get an error, stating I have mismatched delimeters.

this is the code I am currently implementing that is giving me an error:

'\sigma_{D}^{2} ft/sec^{2}'

This is the error I am recieving:

"Invalid expression. Check for missing multiplication operator, missing or unbalanced delimiters, or

other syntax error. To construct matrices, use brackets instead of parentheses."

[Geoff Hayes]

@Matthew Greene - you may want to show more of the code that leads to this error. When I try something like

plot(1:10,1:10)
legend('\sigma_{D}^{2} ft/sec^{2}')

I seem to get the expected results without a warning or error. Can you try the same?

[Matthew Greene]

Not sure what was happening...it looks like I may have missed a comma. It's working now. I appreciate the validation!