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Graphs and Charts

You are going to see a lot of graphs in your time with math. You've already seen them on television, newspapers, and magazines. There are bar charts, line charts, and pie charts. The list goes on. We've got to show you how they work so you can make your own.

When you're starting to work with a grid, you need to know about lines. A horizontal line is one that goes side to side. It's like the line of the horizon in the distance. A vertical line goes up and down. A simple flat grid is made up of horizontal and vertical lines.

Working with Grids

Grids also have numbers or units when you see the lines. Usually you'll see whole numbers starting from 0 (0, 1, 2, 3, 4). There might be negative numbers too. The units go horizontally (left to right) and vertically (bottom to top). There's a special point when both of these labeled lines meet called the point of origin. You will usually find the zero values at the point of origin. The two labeled lines are called axes and they intersect at the zero values.

In math we call the horizontal axis the x-axis and the vertical axis the y-axis. We also call the grid a coordinate plane. A coordinate is a point on the grid. The coordinate plane is the space where all of the possible points can be found. Every point on the plane has a special value. The value comes from the x and y axes. We use the term ordered pair to describe the two values. You'll see ordered pairs written like (2, 5). In reality the ordered pair stands for (x-value, y-value).

Ordered Pairs

When you want to start putting points on the grid, you use the ordered pair to give you directions.

Given ordered pair: (5, 8)
(1) Count five notches to the right along the x-axis from the point of origin (0).
(2) Count eight notches up from the x-axis to the point location of (5,8)

Rules of Movement:
- When you see a positive number for the x-value, move to the right.
- When you see a negative number for the x-value, move to the left.
- When you see a positive number for the y-value, move up.
- When you see a negative number for the y-value, move down.
- When you see a zero in either value, don't move at all.

As you put a bunch of points on a grid, you can connect them with lines. That's pretty easy. When you have more than two points, you can connect them all with lines and create a shape. For example, four points will give you a four sided shape (quadrilateral).

Transformations

Once you get a shape made, you can even move the shape around the plane. Moving the shape is called a transformation. You could slide the shape around and that is called translation. You could turn, spin, or rotate the shape. Ooops. We gave it away because that spinning is called rotation. You could also flip the shape. Think about flipping it to create a mirror image. Flipping is called reflection. You just need to remember those terms and the fact that you can do any one or all of those actions on the original shape you made.

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