How to do kernel or local constant regression?

Hello Mathworks community,

I need to do a kernel regression using the Nadaraya-Watson estimator but I do not know hot to do this. Moreover, I am talking about a surface fit, what makes it even more difficult for me to find an appropriate command. I tried the command fit and smooth but I could not find options to let them do kernel regression.

Could you pleas help me?

Thanks, Marius