That code is going to give you an error, as it does not correspond to any allowed way to call hgsave.
In your previous question I asked you to post the section of code you are doing the saving with, but you did not do so.
The method to convert figures to image files is as given to you already in http://www.mathworks.co.uk/matlabcentral/answers/63850-plotting-within-a-for-loop#answer_75401