Do the boxplot stats without boxplot
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Dear all, I have an enormous number of numbers and I want to plot the box plot
Actually I have 7 sets of 125.000.000 numbers (luckily I am running this in a system with huge ram). As boxplot with 7 inputs takes so much time I was thinking if there might be a way to calculate for every set all the statistics boxplot calculates.. and then feed them in a boxplot_type function to do the stupid plotting.
Is there something like that in matlab?
I would like to thank youf or your help
Best Regards Alex
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Answers (4)
Oleg Komarov
on 13 Aug 2011
Time boxplot:
tic
boxplot(...)
toc
against:
tic
prctile(...)
max(...)
min(...)
toc
and also against:
tic
sort()
toc
for one of your datasets, if there's significant gain for one of the alternatives then yes you could improve boxplotting...but I doubt it.
EDIT
Avoiding to call boxplot on the big database I create a fake boxplot and adjust it with the stats calculated from the real database:
% Suppose truedata is your dataset A
truedata = rand(1e6 + 123423,7);
sz = size(truedata);
% Create fakedata and boxplot it
fakedata = rand(10,sz(2));
h = boxplot(fakedata,'labels',10:10:10*sz(2));
% Now sort your truedata and calculate min,max,25,50,75 percentile
truedata = sort(truedata);
s.mins = truedata(1,:);
s.maxs = truedata(end,:);
xi = bsxfun(@plus,sz(1).*[0.25; 0.5; 0.75], sz(1) * (0:sz(2)-1));
x = [floor(xi(:)); ceil(xi(:))];
s.ptiles = reshape(interp1(x,truedata(x),xi(:)),3,sz(2));
% Readapt the fake boxplot:
% 1.Adjust upper whisker
set(h(1,:),{'Ydata'}, num2cell([s.ptiles(3,:); s.maxs].',2));
set(h(3,:),{'Ydata'}, num2cell(repmat(s.maxs.',1,2),2));
% 2. Adjust lower whisker
set(h(2,:),{'Ydata'}, num2cell([s.mins; s.ptiles(1,:);].',2));
set(h(4,:),{'Ydata'}, num2cell(repmat(s.mins.',1,2),2));
% 3. Adjust body and median
set(h(5,:),{'Ydata'}, num2cell(s.ptiles([1 3 3 1 1],:).',2));
set(h(6,:),{'Ydata'}, num2cell(repmat(s.ptiles(2,:).',1,2),2));
% 4. Delete outlier marking
delete(h(end,:))
7 Comments
Oleg Komarov
on 16 Aug 2011
Use the profiler to check the differences.
Have you tried my other solution?
Alex
on 13 Aug 2011
1 Comment
Oleg Komarov
on 13 Aug 2011
You said 1*125.000.000 sets, what do you mean?
Sorting 1e8 elements takes 11 seconds on my laptop, after that most of the calculations can be done in instants. I really don't see how boxplot is taking som much time.
Please post the code you're using.
Alex
on 14 Aug 2011
1 Comment
Oleg Komarov
on 14 Aug 2011
Please see the edit on my answer and stop creating additional answers, use comments.
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