These data are called variables. In this research the variables are stomatal density and rainfall from January 1st to September 1st. These are two types of variables. The independent variable is data that influences the outcome of the experiment. Often the experimenter has control over this variable.
Time is a very common independent variable.
This data is plotted in the horizontal axis, x axis. In our research Rainfall is our independent variable. The dependent variable depends on the conditions of the investigation, and frequently on the independent variable. The dependent variable is sometimes refered to as the outcome variable. The dependent data is plotted on the vertical axis, the y axis.