Plotting a huge matrix

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Yaser Khojah
Yaser Khojah 2018-9-13
编辑： Yaser Khojah 2018-9-14
I have a big matrix (Supply) with size of 21 X 1000,000 and I want to plot each column against a fixed time vector as
stairs(time, supply)
I have tried to do it with for loop and using the Apps tool box but it is taking forever to run. Is there a fast way to do it?
This is my for loop:
if true
for k = 1:size(supply,2)
stairs(time ,Supply(:,k)); hold on
disp([' ',num2str(k)])
end
Thanks,
  2 个评论
Adam
Adam 2018-9-13
Are you sure you need to plot every value of those 1000000? There is no way that you can distinguish that many values on a plot. Indeed, at that level there aren't enough pixels on the screen to plot them all either. I would recommend sub-sampling your data and plotting that instead. I don't know off the top of my head what is a realistic number of samples to plot that you can visually distinguish, but it would be orders of magnitude less than that.
jonas
jonas 2018-9-13
编辑：jonas 2018-9-13

It could possibly be faster to store the output instead of plotting in each loop. The stairs function will not plot if two output arguments are specified

[x,y] = stairs([1 2 1],[1 2 1])

then you can just plot everything in one go

plot(x,y)

this way, no objects are created until you plot, so the loop should be much faster.

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采纳的回答

Jan
Jan 2018-9-13
Omit the disp command, because updating the command window 1e6 times wastes a lot of time. Setting hold on repeatedly is not efficient also. Then do not create 1 Millions stairs calls, but call stairs with a matrix:
stairs(time, Supply);
But most of all consider Adam's comment: It is very unlikely that this plot is useful, because it has a huge pixel density.
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Steven Lord
Steven Lord 2018-9-14
[Yaser Khojah wrote the following in a flag on Jonah's first comment on this answer. If you want to respond to a comment please add your own comment rather than adding a flag. The intent of flags is to notify contributors with sufficient reputation of potential unclear, off-topic, or spam messages. Thanks.]
I was able to create the plot without the outliers. However, I get this error "Value should be a finite number greater than 0". I think the outliers should be larger than zero.
jonas
jonas 2018-9-14
Sorry that was bad advice from my part. I just noticed that the outliers were not plotted while missing the error message. This should work:
delete(findobj(gca,'Tag','Outliers'))

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更多回答（2 个）

Yaser Khojah
Yaser Khojah 2018-9-13
You are all right but I just wanted to see the whole dense lines. I'm using now boxplot instead since I could not show all the lines
Yaser Khojah
Yaser Khojah 2018-9-14
编辑：Yaser Khojah 2018-9-14
If you do not want to include outliers then use this:
if true
boxplot(y,'symbol','')
end

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