![]() ![]() To graph the logarithmic data, follow these steps: The result should look like the table in Figure 9, but extended all the way to the last year in the table.įigure 9. The natural logarithm is then calculated for cells C3, C4, and so on. Move the pointer to the lower right corner, so that a cross appears in place of the black box in the lower right corner of Figure 8. The formula appears at the top of the worksheet, next to the = sign - see the red rectangle in Figure 8.Ĭopy the formula down the page: Click on cell D2. (The = symbol is used for any calculation in Excel.) You should see the result 2.292535, the natural logarithm of 9.9 (the number in cell C2). In cell D1 of your current table, write Ln Annual CPI. Here is the way to calculate natural logarithms of a data column in Excel: But if we work with logarithms of the CPI, our graph can show details of the entire history. The standard xy-graph does not do justice to the details of change over such a large range. The CPI rose from 2.3 in 1913 to 179.9 in 2002, a change of two orders of magnitude. Furthermore, it is often more revealing to work with the logarithm of data than the data itself. We can, of course, do that linear regression directly by taking natural logarithms of the y data. In the preceding section we observed that the exponential trend curve is determined by doing a linear regression with data points of the form.
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