I am looking to perform a simple linear interpolation to fill a few small gaps in a large data set. The data set tends to be either continous with one or two gaps in it (where I hope to perform the interpolation), or else it has large chunks of data missing where I'd need to return an NA. Also, I'm wanting to perform this on sequential "windows" in the data - ie to return daily interpolated data from a year-long data set, or return an "NA" for a day where insufficienty data is available. This interpolation needs to be performed on a columwise basis (where missing data points in adjacent columns are not related), on a 52000x22 matrix - with windows of 144 each. Can someone please offer some advice, I at m getting confused with the nesting of my loops! I'm using V2.0.1 on linux. Thanks, Laura Laura Quinn Institute of Atmospheric Science School of Earth and Environment University of Leeds Leeds LS2 9JT tel: +44 113 343 1596 fax: +44 113 343 6716 mail: laura at env.leeds.ac.uk