Web-based Plotting for Physics

Summary

For these x-y ('scatter') plots you need:

• Several (say N) pairs of related data: (x_i , y_i ); i=1,2,...,N. The choice of which variable is x (and which is y) can be made on several bases:
  • Which has the least error?
  • Which is the controlling variable?
  • What did your instructor tell you to do? (Note: if you've been told to plot: "A vs. B", B is on the x-axis.)

• Ideally you should have an estimate of the accuracy of the x and y values of the data: the so called x and y-errors (xe_i and ye_i ). The accuracy estimate may be a general rule (e.g., all the y-values are accurate to 3%) or individual estimates for each datapoint. The first thing you will be asked is what sort of errors you have. Making good estimates of errors is perhaps the most difficult part of doing science, however it is not a topic I've written on here: ask your instructor when in doubt!

• What is the current form of your data? Are the numbers already available on this computer (for example in a spreadsheet)? In this case you can probably just copy and paste that data into one of our bulk-entry forms. If your data consist of numbers on a sheet of paper you'll be probably better off using "pointwise" data entry -- in which case I'll want to know how many datapoints you have (i.e., N). In either case, these web pages limit the number of datapoints to N<100. Your errors may be in the form of a formula or a list of numbers.