plot() — Line chart

A line chart that shows how something changes over time.

plot(x, y, type = "l")

Key idea

• A line chart shows how a value changes across an ordered bottom axis, usually time.
• Connected dots make upward or downward trends easy to spot. (e.g. Jan 10, Feb 14, Mar 19, Apr 21)
• You can draw several lines together to compare series side by side. (e.g. Product A vs Product B by month)
• Reading left to right tells the story of growth, decline, or staying steady. (e.g. 100 then 120 then 90)
• Best when the x values have a natural order, not for unrelated categories.

In plain words

It is like a dot-to-dot. Put a dot for each year, then connect them. The line you get tells the story — going up, going down, or staying the same.

Where you'd use it

• A company made $10k, $14k, $18k, $25k over four years. Putting the years on the bottom and profit up the side, plot joins the dots into a line that climbs steadily — an instant picture of healthy growth.
• You have a city’s 12 monthly temperatures. A line chart shows them rising to a summer peak around 30 °C and falling again, making the yearly cycle obvious at a glance.
• To compare two teams over a season, draw both score lines on one plot; where the lines cross you can see the exact match when one team overtook the other.

Worked example 1

Money made (in $1000s) by Manic Mango next to its biggest rival, 2003–2007. A line chart makes the change over time easy to see: Mango keeps going up and passes the rival in 2007 — clearer than bars for the year-by-year story.

Frequently asked questions

When should I join points with a line?

Only when the x-axis has a meaningful order, like time.