ePiX Updates - Easier File Reading

In the past few weeks I have been doing lots of data analysis and graph plotting. I use some graphical tools such as Grace, Veusz and QtiPlot but when doing lots of plots for a big document I wanted something a little more scriptable.

ePiX seemed to fit this bill and when I contacted the author about a few problems I had getting it to work he was very responsive. He is a mathematician whereas I am a physicist and have to handle lots of data in general. So I found the data file reading quite fragile. It does however have some great advantages such as being able to write LaTeX equations right into the graphs and figures.

The image shown above shows a plot of the absorption profile of a gold nanoparticle suspension. In the recent ePiX 1.0.24 release I added a tokeniser to the file reading functions of the data_file class in order to make data file reading more robust and I was able to read all my data files in using a simple loop and plot them as shown.

I have also just finished a data pruning function for the same class, but I am not sure if there is a better way to implement it. It uses brute force right now to iterate through the data and erase unwanted points. It does work well but I am not sure if there is a better way to accomplish its goal using some of the STL algorithms. It does need to delete the whole row though.

  void data_file::prune(double min, double max, unsigned int col)
  {
    // Erase rows where the data is outside of the specified range
    std::vector::iterator> iter(m_data.size());
    for (unsigned int i = 0; i < m_data.size(); i++)
      iter.at(i) = m_data.at(i).begin();

    while (iter.at(0) != m_data.at(0).end())
    {
      if ( *iter.at(col-1) < min || *iter.at(col-1) > max )
      {
        for (unsigned int j = 0; j < m_data.size(); j++)
          m_data.at(j).erase(iter.at(j));
      }
      else
      {
        for (unsigned int j = 0; j < m_data.size(); j++)
          iter.at(j)++;
      }
    }
  }

This pretty much covers the extra bits I needed for data analysis. A nice legend function would be good as drawing legends isn’t as automated as I might like. I would welcome any feedback on the prune function as I think this would make a good addition to ePiX.