Microsoft Office Tutorials and References
In Depth Information
Performing an Exponential Regression
known_y's This is the set of y values you already know in the re-
lationship y = b × m^x. If the array known_y'sis in a single column,
each column of known_x'sis interpreted as a separate variable. If
the array known_y'sis in a single row, each row of known_x'sis in-
terpreted as a separate variable.
known_x's This is an optional set of x values you might already
know in the relationship y = b × m^x. The array known_x'scan include
one or more sets of variables. If only one variable is used,
known_y'sand known_x'scan be ranges of any shape, as long as they
have equal dimensions. If more than one variable is used, known_y's
must be a range of cells with a height of one row or a width of one
column (which is also known as a vector). If known_x'sis omitted, it is
assumed to be the array {1,2,3,...} that is the same size as known_y's.
const This is a logical value that specifies whether to force the
constant b to equal 1. If constis TRUE or omitted, b is calculated nor-
mally. If constis FALSE, b is set equal to 1, and the m values are
fitted to y = m^x.
stats This is a logical value that specifies whether to return ad-
ditional regression statistics. If statsis TRUE, LOGEST returns the
additional regression statistics (refer to Figure 14.16 ) , so the re-
turned array is {mn,mn-1,...,m1,b;sen,sen-1,...,se1,seb;r2,sey;
F,df;ssreg,ssresid}. If statsis FALSE or omitted, LOGEST returns
only the m coefficients and the constant b.
The more a plot of data resembles an exponential curve, the better the cal-
culated line fits the data. Like LINEST, LOGEST returns an array of values
that describes a relationship among the values, but LINEST fits a straight
line to the data; LOGEST fits an exponential curve.
Performing an Exponential Regression
Figure 14.19 shows an estimated population in column B and the generation in
column A. To perform an exponential regression, follow these steps:
11. Because there is one independent variable, the results from the re-
gression occupy two columns, so find a blank range of the spread-
sheet and select a range that is two columns wide by five rows tall,
such as E2:F6.
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