Straight+Line+Graphs




 * || [[image:http://nces.ed.gov/nceskids/createagraph/images/questionmark.gif width="39" height="62" align="left" caption="?"]]Graphs and charts are great because they communicate information visually. For this reason, graphs are often used in newspapers, magazines and businesses around the world.

NCES constantly uses graphs and charts in our publications and on the web. Sometimes, complicated information is difficult to understand and needs an illustration. Graphs or charts can help impress people by getting your point across quickly and visually.

Not sure about which graph to use? Confused between bar graphs and pie charts? Watch the following video for a simple overview: media type="youtube" key="W9BhzvLooI4" height="315" width="420" Need some practical, then log on to the Internet and go to. Here is the link :[|Create a Graph] ||  ||

Getting Started . ..
=Straight-line graphs= Straight line graphs are used in science.
 * Begin by logging on to the Internet and going to if you are not already there.
 * A screen will appear with several options for what type of graph you want to build. If you are unsure of which type of graph you should use, read the [|"How Do I choose Which Graph to Use"] section of the tutorial. Then select the appropriate graph by clicking the icon.
 * Once you have selected your graph, take a moment to read the //Help// menu on the left side of your screen. It will give you some tips about making your graph.
 * "Design"**
 * Once you have selected which type of graph you want to use, you are asked to select several different settings for the layout of your graph. You can always go back and change, so try different options to see which works best.
 * For line graphs and area graphs, you will be asked to select a background color for your graph, the color you want the grid lines to be, the number of grid lines you want (how many segments do you want the y-axis separated into), whether you want the graph to be 2-dimensional or 3-dimensional, and where you want the legend for your graph to be.
 * For bar graphs, you will be asked to select the same things as above, but you will also need to select what kind of bars you want to have.
 * For pie charts, you will need to select what kind of filler you want the slices to have in addition to the general information. Notice you do not have to select information about grid lines, because a pie chart has no x or y-axis.
 * For X-Y plots, you will need to select which type of plot you wish to have in addition to the general information.
 * "Data"**
 * After you have filled in all of the information on the //Design// Tab, you can select the //Data// Tab on the right side of the screen. Again, take a moment to read the help menu. It will explain each of the fields you are being asked to fill in.

Image Source: http://staff.argyll.epsb.ca

Graphs are also used to compare the running costs of vehicles.



Image Source: http://www.algebra-class.com

Graphs visually represent data. Watch the following video on how to produce straight line graphs.

media type="youtube" key="vCeAj4cLPIA" height="315" width="420" Straight-line graphs often represent algebra equations. For instance the equation of a straight-line graph is made up of a y term, an x term, and a number. The following equations are all equations of straight lines: Here are some examples: In a typical question, you will be asked to fill in a table of values, plot them and join them up to make a straight-line graph. Let’s take a look at the line for the rule: y = x + 2. We could also work out other y values using Algebra substitution. We would use the x values -2, -1, 1, and 2 like this: y = -2 + 2 = 0 y = -1 + 2 = -1 y = 1 + 2 = 3 y = 2 + 2 = 4 We could then make these into a set of (x,y) pairs and graph the line: For x = -2, we obtained y = 0, and so our first point is (-2,0) For x = -1, we obtained y = -1, and so our second point is (-1,-1) and so on.
 * y = 3x + 2
 * y + x = 5
 * 2y - 3x = 7

= Using a simple table =

Example:Complete the table of values for **y = x + 3**, and then draw the graph. First you need to complete an equation for each value of x given.

Answers

Choose suitable possible values of x. Six values are usually enough.

With the equation y = x + 3, we have to add 3 to each **x** value to get the the value of **y**.


 * When x = -3
 * y = -3 + 3 = 0
 * When x = -2,
 * y = -2 + 3 = 1
 * When x = 0
 * y = 0 + 3 = 3
 * When x = 3
 * y = 3 + 3 = 6

Once the values of **y** have been worked out, the table looks like this:


 * x || -3 || -2 || -1 || 0 || 1 || 2 || 3 ||
 * y= x +3 || 0 || 1 || 2 || 3 || 4 || 5 || 6 ||
 * y= x +3 || 0 || 1 || 2 || 3 || 4 || 5 || 6 ||

These points can be plotted on on a graph. Each pair of values in the table is an (x, y) co-ordinate - eg (-3, 0) (-2, 1) (-1, 2) (0, 3) etc.

Take a look at the graph y = x + 3 and see how the values are plotted.



==If the question does not ask you to complete a table of values first, you can still create one by making up your own values for **x**. You should work out a minimum of 3 points for a straight-line graph, in case one of them is wrong.==

However, there is an alternative way of doing this process, where we make a Values Table, and do all our working out in the table. We are still doing the same thing, but using a Table to do the Algebra Substitution.

Using a Values Table Method for y = x + 2 We set up a values table for plotting points, but put an extra working out row into it. Because y = x + 2 is a “one step equation” we only need one working out row.

The working out row is shown in light blue below. We also have a green row at the bottom for the plotting points of x and y. Here is how we use the blue row for working out. The next step is to do the working out for each box in the table, and write the answer each time into the purple “Y Value” row. The final step to complete the values table is to write our numbers from the X and Y rows as (x, y) values. We are now ready to plot our (x, y) values onto the Cartesian Plane. We then extend the line, add some arrows to the ends, and create the finished straight line. We also write the original “y = x + 2″ rule next to this line.

You can practise this at the following link: http://www.bbc.co.uk/schools/gcsebitesize/maths/algebra/graphsrev3.shtml[| graphs] And http://graphs.mathwarehouse.com/distance-time-graph-activity.php[| Distance/Time Graphs]