create,table=t,column=a,b;
a=1; b=2;
fill,table=t; ! as usual
a=2; b=4;
fill,table=t; ! as usual
write,table=t;
a=3;
fill,table=t,row=1; ! now the first row is [3 4]
write,table=t;
b=-1;
fill,table=t; ! now the last row is [3 -1]
write,table=t;
setvars,table=t,row=1; ! now a=3, b=4
value,a,b;
setvars,table=t;       ! now a=3, b=-1
value,a,b;