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Re: Graphing d vs t



I'm with you, Tim. Which thing goes on the horizontal axis usually depends
on which variable is considered independent and which variable is dependent
(as you stated). However, it might also be determined simply by what you
are trying to communicate. That is, what are you trying to "look-up" as a
function of what else.

Sometimes it is easier to think of a table rather than a graph, but they're
essentially the same thing. In a table we most likely have the first column
as the column in which we search for some known condition, then we look-up
the corresponding property in the second column. Suppose we have a schedule
for a commuter train running between Chicago's Loop and the outlying
suburbs. It would be most common for the schedule to have the location in
the first column, and the time in the second column. You search for the
station you want in the first column, and see what time the train will be
there in the second column. If I were to graph this, I would put location
on the horizontal axis and time on the vertical axis. However, I could also
imagine wanting the reverse. I might want to pick a time and ask, where is
the train now. In this case I might construct the table and graph
differently, or maybe not, because I can use a table and graph both
directions. But I would be inclined construct the table and graph from the
viewpoint of how I expect people to use the graph or table most often.

If I have a specific use for the graph in my mind, then that determines how
I construct it. If I don't know for sure how people will use it, but I can
identify a dependent variable and an independent variable, I put the
independent variable on the horizontal axis.


Michael D. Edmiston, Ph.D. Phone/voice-mail: 419-358-3270
Professor of Chemistry & Physics FAX: 419-358-3323
Chairman, Science Department E-Mail edmiston@bluffton.edu
Bluffton College
280 West College Avenue
Bluffton, OH 45817