This is a utility function to create a 'graph' data structure to pass to chart module from an 'Excel' sheet
xl2g(xl, ndim = 1, nseries = 1)
has the title and data of the 'Excel' file
is the number of dimensions in the 'Excel' file; it is assumed these are in the first ndim columns of the xl
is the number of series in the 'Excel' file; it is assumed these are in the last nseries columns of the xl