Act 1: Digital Scanning

In this activity, we were to recreate a hand-drawn graph into digital form using a scanned copy of the said graph and a spreadsheet program such as OpenOffice or Excel.
Due to my assumption that linear graphs were ideal for this activity, I opted to use one. Unfortunately, the graph that I got had its axes in logarithmic scale and as a result, accomplishing it was much more difficult than I expected. After exhausting almost the whole period on the graph, I decided it would be much easier to use a different one. Fortunately, Earl had another graph on the second page of his scanned copy, and thus I was able to use it instead. The source of the new graph was Fesbach’s and Lomon’s The Boundary Condition Model of Strong Interactions at page 63. Also, I was told the original graph can be used in the special project since it was challenging, and at the same time, nobody has done it before (as far as I know). In any case, the process goes as follows: The image was cropped in order to isolate the graph from the rest of the scan using Nero PhotoSnap Viewer Essentials. From there, the dimensions of the graph in terms of the number of pixels were recorded.

Since my graph had two parts with different y-axis dimensions, I chose to split and separately accomplish both graphs. For both cases I chose to crop each of the main plots, discarding the values of the axes in the outside. This is because obtaining the pixel coordinates is much easier this way, and at the same time, the cropped images can be readily used as background for the reconstructed graphs later. I recorded the coordinates of the points on the graph as well as a number of representative points for the trend line using MS Paint. Since the axis of the y-axis is inverted, i.e. downwards is the positive direction, I subtracted the obtained values for the y-coordinates from the total height of the image in terms of its pixels. The ratio of the total length of the graph over the total number of pixels was obtained and used as a multiplying factor for the coordinates, which yields the physical values for the graph. The pixel coordinates for both the points and the trend line's representative points are tabulated below:


This was done for both the points and the trend line plot, except that error bars had to be added to the points.

I plotted the points on an X-Y scatter graph using Microsoft Excel. The scales were formatted so that the ticks and the values resemble those which are on the original graph. The two split graphs were then reconnected.

The representative points in the trend line are shown in the image below:

In order to better show the quality of the reconstruction, the plot area’s background was set to the cropped images:

While not perfect, it can be observed that the obtained digital plot resembles the original hand-drawn plots of the book. One of the major problems encountered in the new graph was that I had no idea how to change the y-axis scale. Thus, I simply chose to reconstruct it by accomplishing two different graphs and the grouping the two together.

Overall, I would give myself a grade of 9/10. The graph was reproduced, points, trend line, error bars and all. The main gripe I have is that I used MS Excel 2007 for plotting, which may have made the process tad easier. Also, the scale’s values weren’t the same as the original, but it was merely a matter of visual display and it doesn’t really affect the actual scale of the original graph itself.

Again, loads of thanks to Earl, for giving me the new graph, as well as for Gilbert, for a few tips on the activity, as well as uploading my blog site to the AP186 Google Group.