Thursday, June 18, 2009

AP186, 始まります。 (Activity # 1)


The first activity for Physics 186 is Digital Scanning. Nope, the title might seem too simple but it doesn't end there--it's all about reconstructing images.

We started the activity by looking for some old, rugged hand-drawn plots in some old journals in the library last Tuesday. I picked Figure 11 from H. FESHBACH and E.L. LOMON's Boundary Condition Model of Strong Interactions (MIT, Cambridge), ANNALS of PHYSICS: 29, 19-17 (1964).

We had our plot scanned, and received it through e-mail about a night ago. Today, I started with some cropping and rotating tasks, letting loose my obsessive-compulsive. I figured that I'd have a harder time with it, if I don't crop it in the best way I can now.

After cropping, I loaded the image in paint and took note of the XY locations for the ticks (in pixels) on each of the axes. After which, I noted the XY locations for the points (also in pixels). I used OpenOffice.org Calc for storing my data.


I solved for the difference in the actual physical values and divided it by the difference in the X locations of two ticks. I repeated the procedure for the y-ticks and got the scaling factor needed for the points. I obtained a scaling factor of 0.38 for X and -0.04 for Y.

My actual physical position for the points was computed using : 400+[0.38*(x-value for points)] for X and for Y, 40+[-0.04*(y-value for points)]. Note that an initial value of 400 for X and 40 for Y were applied in order to meet the intercepts of the original plot.

What comes next would be the standard way of plotting XY scatter plots c/o Calc. Nothing special really. I believe that getting the area filled by the original plot would take my reader's attention. In itself, it's not special as well. After all, it's in the Help File (to quote, xD) :

Bitmap
Fills the selected object with the bitmap pattern that you click in the list. To add a bitmap to the list, open this dialog in OpenOffice.org Draw, click the Bitmaps tab, and then click Import.


I autoscaled my plot to make sure that the original image remains unaltered while I tinkered with my plot dimensions. I looked for the best values for my XY dimensions for the plot, added the Axes Titles, and poof! I got a plot that looks just like the image at the right.


Not bad for a first activity. It's actually really challenging to get those points to meet once the AUTOFIT feature is used. Not only can't you use the offset options (the ones you get when TILED is enabled), you also get stubborn sizing options for the Chart Area. But yeah, considering you already know how to do it, it'll probably be done in a matter of minutes. ^_^

I'm definitely getting a 10 for this one. xD

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