# Replace table elements in more than one row

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Davindra Usov on 22 Mar 2023
Commented: Davindra Usov on 23 Mar 2023
Hi,
I have outputted a vector (V) which contains the row indices of elements in a table (T) that contain the string 'rpm'.
T has 3 columns and I initially set all of the elements in column 3 to zero. I now wish to replace all elements in column 3 that have these row indices (so only row 3 and row 7) with a value of 6. I have tried doing this but it doesn't work:
V = [3;7]; % row indices
for i = 1:numel(V)
T(V(i), 3) = repmat(6, numel(V), 1);
end
I get an error saying To assign to or create a variable in a table, the number of rows must match the height of the
table.
Thank you
VBBV on 23 Mar 2023
T = table(zeros(7,1),zeros(7,1),zeros(7,1),zeros(7,1)) % your table
T = 7×4 table
Var1 Var2 Var3 Var4 ____ ____ ____ ____ 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
V = [3;7]; % row indices
T(V, 3) = [repmat({6},numel(V),1)] % put the element in cell array when assigning
T = 7×4 table
Var1 Var2 Var3 Var4 ____ ____ ____ ____ 0 0 0 0 0 0 0 0 0 0 6 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 6 0

Cameron on 22 Mar 2023
You should look into how MATLAB does its indexing. You don't have to loop through the array to change a value. Just do it like this:
T = zeros(10,3); %i just picked 10 rows of data
indx = [3,7];
T(indx,3) = 6
T = 10×3
0 0 0 0 0 0 0 0 6 0 0 0 0 0 0 0 0 0 0 0 6 0 0 0 0 0 0 0 0 0
Davindra Usov on 23 Mar 2023
thank you very much. This works perfectly. The others do as well, however I can only accept one answer

Cris LaPierre on 22 Mar 2023
Edited: Cris LaPierre on 22 Mar 2023
You can, but the code you wrote is trying to replace a single element with a vector, hence the error message.
When you are trying to replace each element with the same value, you do not need to use repmat. Perhaps you are trying to do this?
tb = table(zeros(4,1))
tb = 4×1 table
Var1 ____ 0 0 0 0
tb.Var1([1 3]) = 6
tb = 4×1 table
Var1 ____ 6 0 6 0
% you could also use repmat if you want
tb.Var1([2 4]) = repmat(10,2,1)
tb = 4×1 table
Var1 ____ 6 10 6 10

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