To do this:
1.A number of x and y coordinates in pixel positions of the scanned plot are obtained one by one starting from the left side and listed down in Excel. It must be noted that the origin in Paint is at the top left part.
2. Next, the origin of the scanned plot is noted down and the number of pixel per unit measure in the x and y axis of the original plot is computed to be able to convert the x-y pixel positions to x-y units--use this ratio as the conversion factor.
3. Third, the x-y coordinates for the replotting are computed using the relation of the listed x-y pixels coordinates to the origin of the scanned plot and multiplied by a conversion factor found in 2. This is how:
For the x axis, positive direction (to the right):
x plot=1* (x pixel-x origin) pixel *( measure/#pixel in x)
For the y axis, negative or downward direction:
y plot= -1* (y pixel-y origin) pixel *( measure/#pixel in y)
4. These xplot and y plot coordinates are then plotted in Excel and the picture of the scanned plot is used as the background in Plot area in Excel to superimpose the two to see if the resulting plot coincides with the original using the pixel and units relation.
The figure below illustrates the resulting plot and the table includes the datapoints for the pixels and the corresponding converted values using the formulas in 3.
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Acknowledgement: I would like to give thanks to Kaye for teaching us and Gary in the CS lib on how to go about the pixel and ratio of the units while waiting for our library clearance. :) Also, thanks to Janno for rotation of the image in Nero.
Grade: 10/10. Because I was able to understand and enjoy the activity and superimpose the plots right away. :)
Book: Algebra and Calculus 1912, Palmer
Not bad.
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