Question

Question #d397d

Answer 1

This is an interesting and almost philosophical question. (I was hoping someone else would try to answer it first).

With the qualification that different environments may have their own standards (for example, a business financial graph may often have the X and Y axis flipped compared to what a physicist might expect).

There are two ways to interpret this question:

1. Are there conditions as to what physical quantities can be represented on axis?
   Provided that the quantities along an axis are all of the same type, then any physical quantities may be represented. (As an example of quantities that are not of the same type: "female", "$100,000", and "`H_2O`" would not be appropriate classifications along a single axis).

2. Are there conditions as to which physical quantities should be represented on the X-axis and which on the Y-axis?
   Always allowing for different environment standards, in general (from a mathematical perspective):

If the type of quantities on both axis are discreet then it shouldn't matter (but you are dealing more with a table than a graph).

If one of the types of quantities is quantifiable and the other is discrete, the discrete set of values should be placed along the X-axis. (Note, however, this is commonly reversed in business reports).

If both types of quantities are quantifiable then either representation should be valid except if the relationship between the two sets is a proper function (there is a unique value in one set for any single value in the other set) in which case the set giving rise to the unique value should be graphed along the X-axis.

Answer 2

The dependent variable goes on the Y-axis

Explanation:

An independent variable is one over which you have no control, one good example being Time. Time always goes at the same rate.

If you graph Distance vs. Time, the distance the object goes depends on the speed it was going and the time it travelled, so Distance is the dependent variable.

Since the mathematical Slope of a line is the amount it rises compared to the horizontal distance (the run), any time you are graphing you should consider the way the units are normally expressed; the price of eggs is N dollars/dozen, not N dozen per dollar. In this case, you should show the dozens along the X-axis; you have no control over the number of eggs in a dozen, so it is the independent variable. The total amount you would pay depends on how many dozen you get, so that is the dependent variable.