Matrix "addition" qeustion
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T4H14
am 10 Okt. 2017
Beantwortet: Guillaume
am 11 Okt. 2017
How do I create a matrix A which is equal to a matrix X with column vectors added onto it which are the element wise square and cube of some of the columns of X? I have a matrix that is 32413x46 and I want to take columns 12-18, square them and add them as columns 47-53 to the previous matrix and then take those same columns 12-18, cube them and add them on as columns 54-60.
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Guillaume
am 11 Okt. 2017
Right, you don't have a matrix but a table. Using correct term avoids wasting everyone time. matrices and tables are two completely different things.
All columns of a table must be named. I question the wisdom of adding so many columns to a table, particularly as the value are trivial to calculate whenever you need them, but if it needs to be done, the simplest thing would be to prepend (or append) the names of the existing columns with 'squared' and 'cubed' respectively. This is easily done:
yourtable = array2table(randi([0 100], 20, 46)); %demo table
newtable = [yourtable, ...
array2table(yourtable{:, 12:18} .^2, 'VariableNames', compose('squared_%s', string(yourtable.Properties.VariableNames(12:18)))), ...
array2table(yourtable{:, 12:18} .^3, 'VariableNames', compose('cubed_%s', string(yourtable.Properties.VariableNames(12:18))))]
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Guillaume
am 10 Okt. 2017
If I understood correctly:
A = X;
A(:, 47:53) = X(:, 47:53) + X(:, 12:18) .^ 2;
A(:, 54:60) = X(:, 54:60) + X(:, 12:18) .^ 3;
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Matthew
am 10 Okt. 2017
Here's one possible answer to your question,
%I have a matrix that is 32413x46
X = rand(32413,46);
%and I want to take columns 12-18, square them and add them as columns 47-53 to the previous matrix
X(:,47:53) = X(:,12:18).^2;
%and then take those same columns 12-18, cube them and add them on as columns 54-60.
X(:,54:60) = X(:,12:18).^3;
Another possibility - if you mean "add" literally (as Guillaume answered above)
%I have a matrix that is 32413x46
X = rand(32413,46);
%and I want to take columns 12-18, square them and add them as columns 47-53 to the previous matrix
X(:,47:53) = X(:,12:18).^2 + X(47:53);
%and then take those same columns 12-18, cube them and add them on as columns 54-60.
X(:,54:60) = X(:,12:18).^3 + X(54:60);
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