In my recent posting at
I wasn't precise enough about the handling of the --band option when
the data are supplied in the form of a matrix or matrices.
In fact, this differs depending on whether you are using the
traditional "gnuplot" command or the new(ish) "plot" block. That's
because in the first case the supplied matrix is treated as a mini
dataset (and you index into it for the columns you want), while with
"plot" an initial matrix argument is taken as the data to plot (no
indexing required, or even permitted).
Anyway, here's an illustrative script (based on one devised by Jack
to point out the problem in my exposition, for which thanks):
scalar n = 20
scalar x = 7.5
matrix A = x ~ seq(1,n)' # the data to plot
matrix B = x ~ sqrt(seq(3,n+2)') # the band information
# block style: you need two matrices with --band
end plot --output=display
# traditional style: you select columns of a single matrix
matrix C = A ~ sqrt(seq(3,n+2)')
gnuplot 1 2 --matrix=C --output=display --band=1,3
The two plots should be identical, but they require slightly
different routes for their production.