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Re: Plot colour issue - Strange change of shade

From: Francesco Potortì
Subject: Re: Plot colour issue - Strange change of shade
Date: Thu, 12 Mar 2020 11:33:04 +0100

>I did further research and it appear that other users encountered the same
>issue when plotting a graph using a very large assay. As an example if I
>plot(sin((1:550000)*2*pi/550000), "color", [0,0.45,0], "linewidth", 4)

I see from subsequent messages that the problem is caused by a bug.

However, from a general point of view, asking any plotting program to
draw a line with half a million points is vastly inefficient unless the
plotting is done occasionally (not programmatically).  Depending on what
is the use of your grpah, a reasonable number of points may be 100 for
looking at an educated function on a screen.  Multiply this by 10 if
your function is badly behaved.  Multiply by 10 for publication quality.

Having too many points slows down the plotting routine and creates
postscript files which are much bigger than necessary for publication
quality, and PDF files which are big and slow to render and print.

Should you encounter any of these problems, I suggest using
plotdecimate, from the plot package, which takes points from a line to
be plotted and reduces their number intelligently.

Unfortunately, I see that the plot package is unmaintained and was taken
out of Octave forge.  I specifically miss the tic and the plotdecimate
functions.  Maybe they could be moved to a different package?  Any ideas?

By the way, you can find plotdecimate here:

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