I would suggest using logical indexing (Ch 12 MATLAB Onramp) to select the dates and #Deaths that match the user selection. From there, just plot the corresponding data (Ch 9 MATLAB Onramp). If your dates are imported as datetimes, they will appear as your xticks automaticaly. I'd import the file using readtable (see more here).
Personally, I'd use a live script with a drop-down list (see Interactive Controls) to select the state.
