Plotting a a constant line in a graph

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.

Answer 1

[Iain]

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

Answer 2

[Adam]

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).