☰ Contents · Computing

Review of charts and graphs

Lessons 27 · 1 lessons · B. Boltayev, A. Azamatov, A. Asqarov, M. Sodiqov, G. Azamatova. Fundamentals of Informatics and Computer Technology, Grade 8. Second edition. “O‘zbekiston milliy ensiklopediyasi” State Scientific Publishing House, Tashkent, 2015
27

Review: creating and editing charts and graphs

Textbook: p. 120
GoalSolves chart and graph tasks independently: table, calculation, choice of type, editing and finding mistakes.
New words
area of a square: side · side, written in a sheet as =A2^2 · kvadrat yuzitable of values: a table with the arguments x and the matching y · qiymatlar jadvalisector: one slice of a pie chart; its size shows a share · sektorreadability: how easily a reader understands the chart · o‘qish qulayligi
Explanation

In a review lesson we first make a table, then calculate with formulas and only afterwards build the chart. For example, we find the areas of squares with sides 1, 2, 3, 4 and 5 using the formula =A2^2 and compare them in a column chart: when the side doubles, the area becomes 4 times larger. For a function graph we are given the interval and the step of x: we fill x with the step, write the y formula in the first row, copy it down and make a scatter graph. Readability matters: a pie chart with 12 thin sectors cannot be read, and a column chart is better there. Every chart should have a title, axis names and, if needed, a legend; the colours should be easy to tell apart.

Worked examples
Areas: 1, 4, 9, 16, 25. The column for side 5 is 25 times as tall as the one for side 1 and 25 : 4 = 6.25 times as tall as the one for side 2.
y = –2x + 4, x ∈ [–2; 4], step 0.5: the number of points is (4 + 2) : 0.5 + 1 = 13. At x = –2, y = 8; at x = 0, y = 4; at x = 4, y = –4; the graph crosses the x axis at x = 2.
Class activity

“Chart critic”: groups get three flawed charts (no title, too many sectors, cut axis); they find the flaws and fix them.

Practice
1
What is the area of a square with side 7?
2
How many points are there for y = –2x + 4 if x goes from –2 to 4 with step 0.5?
3
In y = –2x + 4, what is y when x = –1?
4
Why is a column chart better than a pie chart for data with 12 categories?