For the axes in Panel (a), we have chosen numbers that correspond to the values in the table. In drawing a graph showing numeric values, we also need to put numbers on the axes. Notice that in Figure 21.2 “Plotting a Graph” the origin has a value of zero for each variable. The point at which the axes intersect is called the origin of the graph. The rule that the independent variable goes on the horizontal axis and the dependent variable goes on the vertical usually holds, but not always. In other cases, economists simply ignore the rule we will encounter that case in the chapter that introduces the model of demand and supply. In those cases, the variables may be placed on either axis we will encounter such a case in the chapter that introduces the production possibilities model. In some cases, the variables in a graph cannot be considered independent or dependent. The number of passengers thus goes on the horizontal axis the club’s revenue from a trip goes on the vertical axis. Passengers generate revenue, so we can consider the number of passengers as the independent variable and the club’s revenue as the dependent variable.
![drawing two curves on one graph r drawing two curves on one graph r](https://statisticsglobe.com/wp-content/uploads/2020/10/figure-1-plot-draw-multiple-function-curves-to-same-plot-in-r.png)
Recall that, when two variables are related, the dependent variable is the one that changes in response to changes in the independent variable. It is customary to place the independent variable on the horizontal axis and the dependent variable on the vertical axis. The axes should be carefully labeled to reflect what is being measured on each axis.
![drawing two curves on one graph r drawing two curves on one graph r](https://us-static.z-dn.net/files/d2b/4622aabcf1a12baad8322d1786f1bbc1.jpg)
We begin our graph in Panel (a) of Figure 21.2 “Plotting a Graph” by drawing two axes to form a right angle.
![drawing two curves on one graph r drawing two curves on one graph r](https://s3mn.mnimgs.com/img/shared/content_ck_images/ana_qa_image_58c2834542c8c.png)
The two variables shown in the table are the number of passengers taking the bus on a particular day and the club’s revenue from that trip.