So if we create a simple example
C = [-6:6]';E=C;E(1:5)=nan;B=2*C;Table = table(C,E,B)
Table.X(Table.C > 0 & isnan(Table.E)) = Table.B(Table.C > 0 & isnan(Table.E))
C E B X
__ ___ ___ __
-6 -6 -12 0
-5 -5 -10 0
-4 -4 -8 0
-3 -3 -6 0
-2 -2 -4 0
-1 NaN -2 0
0 NaN 0 0
1 NaN 2 2
2 NaN 4 4
3 NaN 6 6
4 NaN 8 8
5 NaN 10 10
6 NaN 12 12
so what is happening in your error is that there is no "filter" for the Table.B but the whole column trying to be fitted into a smaller condition where [Table.C > 0 & isnan(Table.E)]==1;
