wrapper.mvImage: Heatmap of missing values from a MSnSet object
Description
Plots a heatmap of the quantitative data. Each column represent one of
the conditions in the object of class MSnSet and
the color is proportional to the mean of intensity for each line of
the dataset.
The lines have been sorted in order to vizualize easily the different
number of missing values. A white square is plotted for missing values.