Plotting a a constant line in a graph

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Quantopic 2014-8-29

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回答： Adam 2014-8-29

Hi all,

I need for plotting a constant line in a chart in which there is a time series X. So, given the time series X, texting in the command window the code:

plot(X)

I get the time series plot. How can I add to the graph a constant line k = 2? Thanks for help.

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Answer 1

Iain 2014-8-29

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plot(X,ones(size(X)) * k)

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Answer 2

Adam 2014-8-29

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在 MATLAB Online 中打开

plot( [X(1) X(end), [k k] )

would do the job visually if there isn't a reason you need to have a point for every value of your X time series.

Plotting e.g. 1000 points to define a horizontal line is unlikely to result in any kind of performance hit, but is a little un-necessary when 2 points would do just as well.

You can also use:

xlim = get( hAxes, 'Xlim' )
plot( xlim, [k k] )

if you simply want a horizontal line to span the full current x axis range irrespective of whether or not you have clipped the x limits to your X vector (though this is not advisable if you have zoomed in of course as then your horizontal line will be too short when you zoom out again).