[ePiX-users] Histograms

[Andrew D. Hwang]

Hi all,

Marcus' email got me thinking about more featureful data plotting for 
ePiX. Since I rarely plot data myself, I'm asking for user-level feature 
requests and other suggestions or ideas.

My current line of thought has a "data_bin" class, which is created from 
a minimum and maximum value, an optional number of bins (1 by default), 
and perhaps a function that specifies bin widths in some convenient way. 
For example,

  data_bin(0, 10);         // the interval [0,10]
  data_bin(0, 10, 5);      // [0,2], [2,4], ..., [8,10]
  data_bin(1, 8, 3, geom); // [1,2], [2,4], [4,8]; geom(x) = pow(2, x)

Interval divisions can be added manually, e.g.

  data_bin B(0, 10);
  B.cut(3).cut(7); // B = [0,3], [3,7], [7,10]
  B.cut(20);       // out of range, no effect

Data can be read in from a vector of doubles or from a file. Once data has 
been read in, no further interval subdivision is permitted.

  B.read("myfile.dat", 2); // read in column 2
  B.cut(5.5);              // no effect

Draw a histogram with specified vertical scale or area:

  B.histogram();  // defaults to "area = number of data points"
  B.histogram(3); // triple box heights or total area 3...?
  B.histogram(1/B.pop()); // unit-area histogram; B.pop() = population
  B.normalize();  // now histograms will have unit area by default


Are there other features that would be useful? Does the syntax above seem 
natural and easy to use? Are there common or standard ways of dividing an 
interval into bins other than "equal length", and if so, what would be a 
convenient mathematical description? Would it be useful to apply a user- 
specified function to data as it's read in?

Thanks in advance for your input.

--Andy

Andrew D. Hwang                 address@hidden
Department of Math and CS       http://mathcs.holycross.edu/~ahwang
College of the Holy Cross       (508) 793-2458 (Office: 320 Swords)
Worcester, MA, 01610-2395       (508) 793-3530 (fax)