# Extracting data from another column based on row conditions

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Fe on 26 Oct 2022
Commented: Fe on 26 Oct 2022
Hello,
I get an error to extract data from column B as the resulting condition on the left would result to less rows than table B
code:
%create a new column X
Table.X(Table.C > 0 & isnan(Table.E)) = Table.B
Error: unable to perform assignment because the size of left side is 420 by 1 and right side is 497 by 1.
Thanks in advance for any tips you can give me.
BR,
Fe

Joseph Cheng on 26 Oct 2022
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;
Fe on 26 Oct 2022
Hey,
Thanks for thr explanation. Helpful ☺ I did this and works perfectly 😆
Table.X = Table.B Table.X(conditions) = „“
As I needed only entries over there when conditions are not met (mistake in original post)