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Re: Plot scatter points with transparency [message #94589 is a reply to message #94580]

Mon, 17 July 2017 18:56

dg86
Messages: 118
Registered: September 2012

Senior Member

On Friday, July 14, 2017 at 6:00:31 PM UTC-4, ChengYu Xi wrote:
> Is there a way to do transparent scatter plots? (Usually I use cgScatter2D.pro to do scatter plots)
>
> I need to overlay a large number of scatter points in one plot, which consist of several groups. I want to assign different groups with different colors. The problems is they just tend to block each other due to the large number. Is a way to plot them with transparency or any other good solution?
>
> Thanks,
> Chengyu

The plot() function does exactly what you want. Here's a sketch of what you
might want to do:

colors = bytarr(n_elements(x))
p = plot(x, y, linestyle='', symbol='o', $
/sym_filled, transparency=50, rgb_table=34, vert_colors=colors)

Your data points are stored in x and y. The linestyle and symbol options plot the
data as circles that are not connected by lines. The flag /sym_filled fills the circles.
You'll want to choose (or create) a color table. rgb_table=34 is a rainbow table.
The vert_colors is an array of indexes into the color table, one for each point in the
plot. You'll have to figure out what the indexes should be for your data.
Finally, transparency=50 sets each plot symbol to 50% transparency. You'll want
to adjust this number to get the effect you want.

There are lots of other options, and I recommend reading the documentation for
the plot() function.

For what it's worth, the built-in function graphics routines are quite good for making
publication-quality plots.

All the best,

David

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[Message index]

		Plot scatter points with transparency By: chengyuxi34 on Fri, 14 July 2017 15:00
		Re: Plot scatter points with transparency By: Nikola on Sat, 15 July 2017 09:24
		Re: Plot scatter points with transparency By: Med Bennett on Sun, 16 July 2017 22:14
		Re: Plot scatter points with transparency By: Markus Schmassmann on Mon, 17 July 2017 03:56
		Re: Plot scatter points with transparency By: dg86 on Mon, 17 July 2017 18:56

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