How to plot a graph with missing values

Hi! I have a question. I have a matrix with times and observations(East/North/Height), but there are few days where the values are missing. I need to plot them highlighting the existing 'hole' of datas. Moreover, I have to calculate the interpolating line for the existing values so that I cannot divide the datas because I need 1 single model.The graphs that I'm plotting are of this kind.Thank you very much!