Given cout matrix, plot contours

I am trying to recreate what the MATLAB contour, contourf, etc. functions do, except I don't want to create it from a grid. I actually have a vector of contours that is formatted exactly like the cout in the typical function call

[cout,hout] = contour(...)

The first column in cout lists the contour level and number of points that define the contour (for example [55;337] which means that the first 55-dB contour has 337 points). Then after the next 337 columns of X-Y coordinates, I get the next contour (for example [60;123] which means 60-dB contour has 123 points).

In essence I want to reverse the process. This format is how MATLAB stores the data to create contour plots, but I want to plot the contours given that I have them stored in the proper format in the cout handle.

The key here is that I have multiple contour "islands" (i.e. two distinct contours associated with the same decibel level) and I want to be able to plot them together as one contour with a single label, but without trying to connect them. If I had the grid, I would just use the contour function and let MATLAB's internal functions take care of the contour formatting. But I only have the vector of contour coordinates.

I tried to open the contour function's source code in MATLAB to see how they do it, but this just calls another function contourHGUsingMATLABClasses. I tried to open this one and I could not access it.

Any help would be much appreciated.