Hi, I am analysing a data set which has missing incensities corresponding to one specific print-tip for all slides. I want to do printTipLoess normalization using maNorm() function from marrayNorm package. It did not work for my data set and I am getting the following error message: > dat.Norm = maNorm(dat.RAW, norm="p") Error in simpleLoess(y, x, w, span, degree, parametric, drop.square, normalize, : invalid `x' Is there any way to use maNorm() successfully for this kind of data set. Thanks in advance, Mahbub.