Figuring out the most fitting prefix for a vector dataset
显示 更早的评论
Hello fellow Matlab users,
I'd like to ask for your advice concerning a numerical topic. So I mainly use Matlab for simulation purposes (electrical circuits). My simulations return vectors containing state variables and power / energy quantities. I'm trying to fully automate a report generation with Matlab code but I'm facing a small problem. I'd like to determine the best prefix for a data set. So for example I get a vector with 1000 values. My initial idea was to get the exponents through a mathematical trick floor(10log10(vect)) and then calculate the mean of the vector containing the exponents, which would give me the mean exponent. From the exponent I can determine the nearest prefix (milli, micro...) . My problem is that some simulations return values with an accuracy of 10e-80 which totally falsifies the mean. So do you guys have any idea on how to basically get the mean exponent of a vector dataset ?
I appreciate all your thoughts and answers
6 个评论
Adam Danz
2020-5-28
What about mode() instead of mean()? Median is better than mean, too.
Bakr Al Beattie
2020-5-29
Ameer Hamza
2020-5-29
What about ignoring the zeros and use the median value as suggested by Adam
median(nonzeros(x))
Bakr Al Beattie
2020-5-29
Adam Danz
2020-5-29
So, try it out, then.
median(x(abs(x)>1e20)) % play around with the threshold value.
If that doesn't work, plot the vector of values and show us the results. Something like this would be useful
figure()
subplot(2,1,1)
plot(y,'o-')
subplot(2,1,2)
histogram(y)
Bakr Al Beattie
2020-6-5
编辑：Bakr Al Beattie
2020-6-5
Sorry for the late replay but I have been a but busy this past week. So I tried your suggestions and still get the same problem. E.g.
So this is a histogram for one dataset. The corresponding plots:
Specifically, the histogram corresponds to the orange graph in the subplot(3,1,1). But the same problem is still existent in all plots. As can be seen, there is a long period where the data can be zero. Even when I filter out every exponent above abs(10^24), my prefix is still falsified.
Edit: here is the code I use:
function Exp = getExponent(Var)
vecWithExp = abs(floor(log10(abs(Var))));
vecWithExp = vecWithExp(~isinf(vecWithExp));
vecWithExp = vecWithExp(abs(vecWithExp) < 24);
meanExp = median(vecWithExp);
vecWithSign = floor(log10(Var));
sign = round(mean(vecWithSign(~isinf(vecWithSign))));
if isempty(meanExp)
Exp = 0;
else
Exp = sgn(sign)*round(meanExp);
end
end
回答（1 个）
Adam Danz
2020-6-5
There are no axis labels on the histogram so I'm not sure what it represents. If it represents a distribution of y-values for the orange line in the first subplot, I'd expect a giant bar at x=0 but I don't see that.
I don't undersant what the problem is with taking the median of values greater than some very small number.
m = median(vector(abs(vector)>0.001));
You can play around with the threshold value. If you zoom into the axes using ylim([-.001,.001]) you can see whether all of the undesired data fall into those limits.
类别
在 帮助中心 和 File Exchange 中查找有关 Creating, Deleting, and Querying Graphics Objects 的更多信息
2020-5-28
2020-6-5
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!
Translated by 
