I don't even know what that means. Basically to get a spectrum from some row and column, you can do
thisSpectrum = multspectralImage(row, column, :);
plot(thisSpectrum, 'b-', 'LineWidth', 2);
If you want, you can plot the spectra for every single pixel in the image. You can even get the average spectra if you want, though I imagine you'd do that for some sub-regions of the image that look different rather than for the whole image.
If you're thinking of something like what colorcloud() does to plot the RGB color gamut, then no, you can't do that. You can't have a scatterplot with 151 different axes, only 2 or 3. I suggest you do cluster analysis instead to find the "clumps".