ExpReg problem

[Fred Nurk]

Menu -> Statistics -> Stats Calculations... -> Exponential Regression.
I type {0, 1, 2, 3, 4, 5} into X List: and {0, 1, 3, 7, 15, 31} into Y
List and press Enter twice. It comes up with Domain Error. Why?
Shouldn't it come up with a table of results indicating 2^x - 1?

[Jan Honnens]

It doesn't like the point (0,0) for functions of the form f(x)=b*a^x
E.g. add 1 to the y-values and then use Exponential Regression to obtain f(x)=2^x

[Nelson Sousa]

an exponential regression is in simply a linear regression between the
xlist and ln(ylist). As ln(0) means trouble... you get the domain
error.

In fact, regressions are "all" linear (except the sinusoidal and
logistic): quadratic, cubic and quartic correspond to several (2, 3 or
4 resp.) linear regressions with dummy variables, while exponential,
power and log regressions are linear regressions with some
manipulation of the original data lists ( xlist vs. ln(ylist), ln(x)
vs. ln(y) and xlist vs. exp(ylist) resp.)

Cheers,
Nelson