[GRASS-user] Failed to draw barscales to some frames

[sgw00412 at nifty.com]

I'm grass beginner user from Japan.

I tried to three maps on a monitor with command "d.frame".

I was able to draw three maps successfully.
However, I failed to add the barscale in the second and third maps. 

Why is it so ?

My scrips as follows;
---
d.mon x0

#step.1
g.region vect= area_A
d.frame -c at=51,100,0,70
d.vect .....
d.vect ....
d.barscale bcolor=white tcolor=black at=0.0,0.0
# barscale was drawn

#step.2
g.region vect= area_B
d.frame -c at=0,50,0,50
d.vect ....
d.vect ....
d.barscale bcolor=white tcolor=black at=0.0,0.0
# barscale was not drawn...why ?

#step.3
g.region vect=area_C
d.frame -c at=0,50,51,100
d.vect ....
d.vect ....
d.barscale bcolor=white tcolor=black at=0.0,0.0
# barscale was not drawn...why ?
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Yasuo shimada : Japan weather association, tokyo office.