Gnuplot timeseries

Ruby
1

Does anyone have an example of plotting a timeseries with gnuplot and
setting the xrange? Why doesn’t the following snippet work as expected?
It produces the attached.

require ‘rubygems’
require ‘gnuplot’
require ‘date’
obs_times = Array.new
data = Array.new
24.times { |h| obs_times << DateTime.new( 2009, 1, 1, h ); data <<
rand() }

doesn’t work either

24.times { |h| obs_times << “2009-1-1 #{h}:00:00”; data <<

rand() }

Gnuplot.open do |gp|
Gnuplot::Plot.new( gp ) do |plot|

causes error plot.xrange

“[“2009-01-01T00:00:00+00:00”:“2009-01-01T23:59:00+00:00”]”
plot.data << Gnuplot::DataSet.new( [ obs_times, data ] ) do |ds|
ds.with = “points”
ds.linewidth = 4
end
end
end

2

causes error plot.xrange

“["2009-01-01T00:00:00+00:00":"2009-01-01T23:59:00+00:00"]”

I’m not sure where the +00:00 comes from.

This post…

O'Reilly Media - Technology and Business Training

…shows how to format the time and build a range:

def timefmt; ‘%Y/%d/%m-%H:%M’; end

def fetch_codelines(stat, fields)
return stat.values_at(*fields).map{|values| values[‘codelines’] }.sum
end

def ftime(timestamp)
Time.at(timestamp).strftime(timefmt)
end
…
plot.xrange “[‘#{ ftime(mini) }’:‘#{ ftime(maxi) }’]”

I admit the documentation on that technique, in both Gnuplot.rb and
gnuplot,
are very scarce!

3

Phlip wrote:

causes error plot.xrange

“["2009-01-01T00:00:00+00:00":"2009-01-01T23:59:00+00:00"]”

I’m not sure where the +00:00 comes from.

That’s the default format of DateTime.new.to_s

This post…

O'Reilly Media - Technology and Business Training

…shows how to format the time and build a range:

def timefmt; ‘%Y/%d/%m-%H:%M’; end

def fetch_codelines(stat, fields)
return stat.values_at(*fields).map{|values| values[‘codelines’] }.sum
end

def ftime(timestamp)
Time.at(timestamp).strftime(timefmt)
end
…
plot.xrange “[‘#{ ftime(mini) }’:‘#{ ftime(maxi) }’]”

I admit the documentation on that technique, in both Gnuplot.rb and
gnuplot,
are very scarce!

Thanks for the ideas. Ruby originated gnuplot examples are so scarce
that I’ve been looking (in vain) for another package that as lightweight
but better documented.