Huge Execution Time Discrepancy with line() Command

Question

Eric 2012-1-14

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/26084-huge-execution-time-discrepancy-with-line-command

The following code takes no more than 4 seconds to execute:

figure(statfig);
set(gcf,'Position',get(0,'ScreenSize').*[1 1 0.5 1]);
titlestr = [test ' - Statistics - ' num2str(rpmval) 'RPM - ' samplestr ' - ' upper(sensor)];
subplot(size(detdata,2),1,var);
plot(detdata(:,var)');
hold on;
% line([1:length(detdata)],avg_env_sample(var),'Color','r');
% line([1:length(detdata)],avg_env(var),'Color','g');
hold off;
% legend('Detrended Data','Envelope','Envelope Mean');
title([titlestr ' - ' varname]);
xlabel('Sample [n]');
ylabel([varname ' [g]']);
set(gcf,'Name',titlestr);

With the commented code uncommented, execution time goes up to two minutes. Similar code is executed 3 other times (without the line commands) without a problem.

Any suggestions?

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Eric 2012-1-14

16000

Eric 2012-1-14

But plot() gets executed on that sized data many (hundreds) of times, with no issues.

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Answer 1

Rob Graessle 2012-1-14

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https://ww2.mathworks.cn/matlabcentral/answers/26084-huge-execution-time-discrepancy-with-line-command#answer_34093

在 MATLAB Online 中打开

Are you expecting each call to 'line' to draw 15999 lines or just one line? If it is the latter, try this instead:

line([1 length(detdata)],avg_env_sample(var),'Color','r');
line([1 length(detdata)],avg_env(var),'Color','g');

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Walter Roberson 2012-1-14

It appears to me that var is a scalar, as otherwise the subplot() would not work. Then in order to draw a horizontal line, the y coordinate would need to be duplicated:

line([1 length(detdata)],avg_env_sample([var var]),'Color','r');

line([1 length(detdata)],avg_env([var var]),'Color','g');

Eric 2012-1-14

So my understanding is this will draw a horizontal line interpolated from two (x,y) points instead of a 16000 point line? I still don't understand why the execution of the original code is so slow if plot() executes so quickly on the same sized data. But it does bring everything back to normal. Thank you Walter and Rob.

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