plot output function

Hi,

I have written my own function to estimate a local linear regression.
When I plot the output vector on the scatterplot of the data, the
function lines does not work and I get a rescaled regression line. 
When I plot the output vector alone, the graph looks right, but choosing
the type "line" instead of the default does not deliver a clear single
line.

Does somebody know why this is happening.

Thank you,

Chiara