Data tables and bar graphs are used to track and represent how two variables interact. Generally, a bar graph is made from data entered into a table. Use graph paper to draw the graph by hand, or use a program like Microsoft Excel, which draws graphs after data is entered into a spreadsheet.
- Skill level:
- Moderately Easy
Things you need
- Graph paper
- Microsoft Excel
Determine the two categories, or variables, being compared. For example, you could keep track of the changing temperature outside in a bar graph using "Temperature" as one variable and "Day of the Week" as another.
Draw a grid on the graph paper with two columns: one for "Temperature," one for "Day of the Week." The grid will have as many rows as there are days that you took data. If you tracked temperature for all seven days of one week, the grid would have two columns and seven rows. Enter the data into the appropriate squares. This is your data table.
Draw two intersecting lines on your graph paper, one straight up and down, one horizontal. This is your X-Y axis, with the horizontal line representing "X" and the vertical line representing "Y." Where the two intersect is known as the origin, where all data is zero. Anything below the X-axis is negative, and anything to the left of the Y axis is negative. For the temperature graph, there is no negative data, so you simply need to draw the top half of the Y axis and the right half of the X axis, meeting at the lower right to look like an L shape.
Designate one variable as X and one as Y. For the temperature graph, it would be best to designate the day of the week as X. This way the bars will rise vertically, as opposed to being drawn horizontally. Along the X-axis, make tick marks spread equally apart to designate each day of the week. Along the Y axis, make tick marks to show the scale for temperature. For example, every three boxes on the graph paper could equal -15 degrees C. Although the corner of the graph technically represents zero degrees, if your lowest measured temperature was, say, 65, make your first point 15.5 or 18.3 degrees C and measure from there. Otherwise, the graph would become disproportionately tall and would have a lot of wasted space.
Use your data table to plot the points on the bar graph. If it was 75 degrees on a Tuesday, plot one point that sits at both Tuesday and 75 on your graph. Do this for each set of data. Then draw a bar for each day with its base on the X-axis and its top at the plotted points. Fill in the bars any way you like.
Making Tables and Graphs by Hand
Open a blank spreadsheet in Excel. Make a data table on the spreadsheet the same way you did for the graph paper. Simply type in the column headers ("Temperature" and "Day of the Week") in two squares next to each other, and type the data in the squares below.
Highlight all of the data, excluding the category titles, and click the Chart Wizard icon, which has a picture of a bar graph on it.
Under Standard Types, choose "Column," for a vertical bar graph. Hit "Next." Hit "Next" again. (Highlighting the data eliminates the need for this step.)
Enter the labels for your X and Y axis, and choose a title for the graph. Click "Next."
Choose if you would like the chart to appear in your current spreadsheet, or if you would like to open a new one. Click "Finish." To customise your graph, double-click on the finished graph. A menu will open that allows you to change the colours and appearance of the graph.
Using Microsoft Excel
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