Line graphs are used to visualize the trajectory of one numeric variable against another. Unlike scatter plots the x- and y-coordinates are not visualized through points but are instead connected through lines. Line graphs are most typically used if one variable changes continuously against another numeric variable which is the case for most time series charts (e.g. prices, customers, CO2 concentration, temperature over time), continuous functions (e.g. sine
sin(x)) or other near-continuous relationships (real-world supply/demand curves).