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Physics Practicals

About Datasets

The Physics Practicals have a standard format for all datasets.  Most locally written software automatically can read and write datasets using this format. Examples of locally written sofrtware include CreateDataset, ViewDataset, and PolynomialFit. Here we describe what that format is.

The dataset file is text.

  1. The first line of the file is the title of the dataset.
  2. The second line of the file names the variables of the data. The names are separated by tabs. In the examples below we represent a tab with: <TAB>
  3. The third and subsequent lines of the file contain the data. Each datapoint is on a separate line and the values are separated by tabs.

Thus, the dataset can be edited with a text editor or a spreadsheet program such as Excel. There are four cases for the number of variables in the dataset.

One Variable

If only one value is given for each datapoint, it is the dependent (i.e. y) variable. In this case the values of the independent (x) variable are assumed to be 1, 2, 3, … in order.

Here is an example of such a dataset:

Balonium decay values
Counts per second

Two Variables

In this case the first column contains the values for the independent (x) variable and the second column the values for the dependent (y) variables. For example:

Student collected data on pressure-temperature values
Pressure (cm Hg)<TAB>Temperature (C)

Three Variables

If there are three variables, the third one is the uncertainty in the dependent (y) variable.

Thermocouple Calibration Data
Temp (C)<TAB>Voltage (Volts)<TAB>errV

Four Variables

Now there are explicit uncertainties in both coordinates of the data. The first column contains the name and values of the independent (x) variable, the second column contains the name and values of the uncertainty in the independent variable, the third column contains the name and values of the dependent (y) variable and the fourth column the name and values of the uncertainty in the dependent variable.

Pearson's Data with York's Weights

This document was written by David M. Harrison, Dept. of Physics, Univ. of Toronto in December 2007.