Line graph
Topic: Graphical Representation of Data and Thematic Maps · NCERT: Class 12, Ch 3 "Graphical Representation of Data"
Meaning
A line graph marks values as points and joins them with a line. Time goes on the X-axis (the horizontal line) and the values go on the Y-axis (the vertical line). It is best for time-series data, which means data recorded again and again over time. Examples are temperature, rainfall, population growth, and birth and death rates. To draw one, round off the data, choose a scale that covers every value (including any negative ones), plot the points and join them freehand. The rise and fall of the line shows the trend clearly.
Example
NCERT plots India's annual population growth rate. It was 0.56% in 1911. In 1921 it fell to −0.30%, the only negative decade. It peaked at about 2.2% in 1971–81 and fell to 1.79% in 2011 (NCERT figure).
Don't confuse with
- Polygraph: a line graph has a single line for one variable. A polygraph has several lines, so it can compare several variables on one graph.