Heatmaps in Ruby

Ruby
1

Hi,

I am currently thinking about doing a heatmap for data visualization,
but I have very little experience with any type of graphical tools in
ruby (like the various SVG libs etc).

So I was hoping someone could point me in the right direction and save
me some time trying out useless libraries :wink: Doesn’t have to be ruby
either, but that way I could probably integrate it more easily into my
analysis pipeline.

Thanks,

Marc

2

On Thu, Nov 26, 2009 at 8:43 AM, Marc H.
[email protected] wrote:

http://blog.revolution-computing.com/2009/11/charting-time-series-as-calendar-heat-maps-in-r.html

I think there are ruby bindings for R too, so that may help.

Best regards,
Michael G.

3

Hi,

thanks for the link - I suspected that R would probably have that
functionality. At this point I am simply curious how to do it in ruby.

I managed to write a simple program that uses RMagick to draw an
intensity map. It takes the highest observed value, sets it to 100% and
then draws other values in relation to that.

What I don’t know is how to write a method that, based on a numerical
value, determines a color, i.e. from blue to red.

So if for example the value ‘1’ should be a deep blue and ‘100’ a bright
red - how would one do that? All color coding schemes allowed!

RMagick can draw colors using a cmyk notation (c,m,y,k) in percent as
well as rgb or the commonly found code in css files ala #00cc33 .

Am interested in all suggestions :wink:

4

On Fri, Nov 27, 2009 at 13:49, Marc H.
[email protected] wrote:

What I don’t know is how to write a method that, based on a numerical
value, determines a color, i.e. from blue to red.

So if for example the value ‘1’ should be a deep blue and ‘100’ a bright
red - how would one do that? All color coding schemes allowed!

Hi,

what you are looking for is “color ramp” or “color gradient”, there
are many sites with algorithms
how to compute colors between two or more given ones (for example from
blue to red).

J.

5

Hello,

Am interested in all suggestions :wink:

You could be interested in Tioga which can do exactly what you are
looking for. See the many examples given in the tutorial.

http://www.itp.ucsb.edu/~paxton/tioga.html

Cheers,