When you create a graph using the Google Docs spreadsheet program, most of the graph types require that the "Y" axis be a numerical scale to properly display the data. However, the "XY Scatter" chart type will let you define both the "X" and "Y" axes and then plot the point where your data intersects each axis. The scatter chart always uses the first column as the "X" axis, so if you need to swap the two axes, you will need to change the order of the columns on your spreadsheet.
Visit the Google Docs website at Docs.google.com. You may be prompted to log in to your Google account by providing your email address and password. Select the spreadsheet with your chart from the list of available spreadsheets on the Google Docs landing page.
Right-click on the letter above the second column, which is the one that you want to make into the "X" axis. Choose "Cut" from the drop-down menu.
Right-click on the letter above the first column and choose "Insert 1 Left" from the drop-down menu. Right-click the letter above the new column and choose "Paste."
Click the name of your chart, which is displayed in the upper left corner of the chart window. Choose "Edit Chart" from the drop-down menu. When the Chart Editor window appears, click and drag on the top of the window to move it off of the columns that you are working with.
Click on the top cell in the first column of your data. The Chart Editor window will minimize. Click and drag the cursor down until you reach the bottom cell in the second column, then click "OK" in the minimized Chart Editor window. Click "Update" in the Chart Editor window. The "X" and "Y" axes are now swapped on your chart.