(1) Importance
* A graph representing the quantitative relationship between related quantities with dotted lines is called a statistical graph.
(2) Classification
1. Bar chart represents a certain quantity with unit length, and draws straight lines with different lengths according to this quantity, and then arranges these straight lines in a certain order.
Advantages: It is easy to see the quantity of each. Note: When drawing a bar chart, the width of the bars must be the same. Take the unit length to express the quantity, depending on the specific situation;
The straight lines representing different items in the composite bar chart should be distinguished by different lines or colors, and the legend should be displayed below the drawing date. General steps to make a bar chart:
(1) Draw two vertical rays according to the drawing size.
(2) On the horizontal ray, reasonably distribute the position of the strip and determine the width and interval of the straight line.
(3) On the deep line perpendicular to the horizontal ray, according to the specific situation of the data size, determine how much the unit length represents.
(4) Draw straight lines with different lengths according to the data size, and indicate the number.
2. The broken line statistical chart represents a number with unit length, draws points according to the number, and then connects the points with line segments in turn. Advantages: it can not only represent quantity, but also clearly represent the change of quantity. Note: When the horizontal axis of the broken line statistical chart represents different years, months and other times, the distance between different times should be determined according to the interval of years or months.
General steps of making broken-line statistical chart:
(1) Draw two vertical rays according to the drawing size.
(2) On the horizontal ray, the positions of broken lines are appropriately distributed, and the width and interval of straight lines are determined.
(3) On the deep line perpendicular to the horizontal ray, according to the specific situation of the data size, determine how much the unit length represents.
(4) Draw all points according to the data size, and then connect them with line segments in turn, and indicate the quantity.
3. The fan-shaped statistical chart represents the total with the area of the whole circle, and the fan-shaped area represents the percentage of each part in the total. Advantages: It clearly shows the relationship between each part and the whole. General steps of making industry statistical chart:
(1) Calculate the percentage of each part in the total first.
(2) Calculate the degree of the fan-shaped central angle representing the number of each part.
(3) Draw a circle with an appropriate radius, and draw all sectors in the circle according to the central angle calculated above.
(4) In each sector, indicate the number name and percentage of each part, and distinguish each sector with different colors or stripes.