Plot divergent stacked bar chart

[Joao Rodrigues]

Dear all

I would like to know if it possible to plot a divergent stacked bar 
chart in Octave.

As an example consider the dataset a =  [
10    8
5    -3
-7    -1
]

I want to have two stacked bars, where:

the first has blue from 0 to 10, green from 10 to 15 and red from 0 to -7;

the second has blue from 0 to 8, green from 0 to -3 and red from -3 to -4.

Additionally, the net total should be displayed as a dot in positions 8 
and 4, connected by a line if I so wish.

The cherry on top of the cake would be to be able to choose a divergent 
y-log scale too.

Is there any way to do this?

I tried bar(a','stacked') but the negative/positive values are all 
stacked on top of one another, overlapping the other values. (e.g., in 
the first row it yields blue from 0 to 8 and red from 8 to 15.)

Thanks
joao