Multiply matrices of different sizes
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Background: I've got 7 years worth of Power data for a wind farm binned into 100 bins of wind speed i.e. 100 x 7 matrix. I've got probability of each of that bin happening i.e. 100 x 1 matrix. I would like to multiply the elements of 100x7 matrix by elements in a 100x1 matrix to get cumulative probability of power output.
In simple term: how do I multiply 100x7 matrix by 100x 1 matrix? Tried bsxfun but didn't work.
2 个评论
Jan
2018-3-16
"Didn't work" is a weak explanation. Better post your code and the complete error message. Not that bsxfun will be the solution, so letting us guess, what fails in your case, is not useful.
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Jan
2018-3-19
编辑:Jan
2018-3-19
Your code:
for yrs = 1:length(years)
[N,edges,bin] = histcounts(SPEED(:,yrs),100);
COUNT = N.'; % Here [] is a waste of time
nelements = sum(COUNT);
prob_bins = COUNT ./ nelements;
Area = bsxfun(@times, Pow_ave(:,yrs), prob_bins);
end
Area is overwritten in each iteratotion. Maybe you want:
Area(:, yrs) = Pow_ave(:,yrs) .* prob_bins;
As far as I can see, Pow_ave(:, yrs) and prob_bins are both 100x1 vectors, so there is no need for bsxfun.
2 个评论
Jan
2018-3-19
@NMans: Pre-allocate theoutput before the loop:
Area = zeros(100, 7);
This avoids the iterative growing of the array, which is expensive in general - although the runtime will not matter much in this case.
更多回答(1 个)
Geoff Hayes
2018-3-14
NMans - if you want to multiply each column of the 100x7 matrix by the 100x1 matrix, then you could use bsxfun as
X = randi(255,100,7); % generate some dummy data
Y = rand(100,1);
Z = bsxfun(@times,X,Y);
Or are you trying to do something else?
3 个评论
Geoff Hayes
2018-3-16
NMans - when I run the code that I posted in my answer, Z is a 100x7 matrix. Are you sure that your answer is 100x100?
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