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How to Use Log Graph Paper

Logarithmic graph scales are often used when plotting data that demonstrates an exponential relationship. An exponential relationship is of the form y = a * x^b where "x" is the independent variable on the x-axis, "y" is the dependent variable on the y-axis and "a" and "b" are constants.

You might need to plot an exponential function on logarithmic graph paper. On a linear scale, plots of exponential relationships yield curves, but on a logarithmic scale they yield straight lines. It is significantly easier to determine the values of the constants "a" and "b" from a straight line rather than a curve.

Instructions

- 1
  Understand that on the graph paper, every 10 grid lines is called a "cycle" and represents one factor of 10. Each line is labelled from 1 to 9, then 0, with the spacing between each gradually decreasing.
- 2
  Relabel the lines so that the scale for each axis is appropriate for the range of data you want to plot. For example, if you want to plot data on an axis from 20 to 900, relabel the first cycle to "10, 20, 30 ... 90" and the second cycle to "100, 200, 300 ... 900, 1,000."
- 3
  Plot your data points on the graph, taking care to remember that each cycle represents a factor of 10. Double-check that your points are correctly plotted.
- 4
  Label your axes with an appropriate title, including the units, and give the graph a descriptive title.

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