How to visualize time-series data?

Question

I have some time-series data I want to visualize as 2d plot.

The input is ISO-date-format and value separated by space, one record per line:

2010-10-21 23
2010-10-22 32
etc.

The output should be a nice looking 2d plot. Basic requirements:

• output to a X11 window (as preview) and to a png file
• x-axis has to understand the dates and naturally scale the data, e.g. a gap between 3 days should be three times as long as a gap between 1 day
• should be callable from a script
• nice output and convenient to use

Bonus:

• svg output

I tried gnuplot and it works - it has some date support:

gnuplot> set xdata time
gnuplot> set timefmt "%Y-%m-%d"
gnuplot> plot "test.dat" using 1:2

But I have some problems with gnuplot:

• with default settings plots look very ugly
• it is difficult to find stuff in the manual - e.g. when plotting points how do I use small filled circles instead of the default '+' sign?
• the gnuplot shell is a pain in the neck - it does not use readline, it is broken, command completion is a joke, I don't know how to enable vi shortcuts - or if they are supported, what about reverse search etc.

Thus my question: What are the alternatives for visualizing time-series data?

Or am I overstating the gnuplot issues?

Answer 1

R is better at this sort of thing than Gnuplot because:

1. It's a complete programming environment, with C and Fortran-compatible extension APIs. If your computer can do a thing, you can do it with R.

2. Many have already contributed their solutions to common problems to the CRAN: Comprehensive R Archive Network. You might find the zoo and ggplot2 packages helpful for this task.

3. There are many books on time series analysis and R in general.

R has everything you asked for:

• Outputs to X11, PNG, or (with an add-on) SVG

• Filled circles for plot points: pass pch=19 or pch=20 to par() or points(). There are many other plot point symbols predefined, plus all of Unicode if you're using a font with Unicode support.

• Time-aware charting: if the built-in ones don't have the scaling you want, you can build anything you need with R's plotting primitives

• Callable from a script: use a #!/usr/bin/Rscript shebang line on your R program file

• Nice and convenient: There are GUI frontends, if you like, and if you don't like, the default command-driven environment has a lot of nice features, like the ability to see the R source code of many builtin operations, which helps to learn how the system is put together. (Yes, much of R is written in R!)

• Pretty plots: Antialiasing is the default if R is built against Cairo, which it will be if it's a recent build on Linux. Old versions of R may not have AA built in. For an idea of the capability of R if you put a bit of time into it, check this out:

  

  (Click image for article describing it.)

Regarding the gnuplot command line, you can build it to support GNU readline, BSD libedit, or as a fall-back, a custom built-in command line editing scheme. (This according to p.20 of the manual.) I have gnuplot 3.7 on one machine and 4.0 on another, and they're both built with readline. Is your binary built without any of these?

Answer 2

RRDTool's whole purpose of existence is plotting time series data, but it's primarily meant for automated graphing and may not be the best fit for your needs.

That said:

• It can output in either PNG or SVG, but has no preview functionality.
• Time-scaling is built in.
• Easily scripted (command line access or libraries in many scripting languages).
• Output can be made to look pretty decent .