background subtraction

while background subtraction i am facing a problem that whole body part of a person is not getting segmented as a whole and thus its centeroid is shifting more than i expecting.How to deal with this problem.I can some1 help me out with some example of code

[Ryan]

http://www.mathworks.com/matlabcentral/answers/7924-where-can-i-upload-images-and-files-for-use-on-matlab-answers

/Walter Roberson.

[Walter Roberson]

What is class() of the data you are subtracting, and which subtraction operation are you using? For example are you using imsubtract() ?