# NLREG - Nonlinear regression & curve fitting program

nr440 at aol.com nr440 at aol.com
Wed Mar 29 07:56:39 EST 2000

```    ** Announcing NLREG -- Nonlinear Statistical Regression Program **

http://www.nlreg.com

NLREG is a powerful statistical analysis program for Windows 95/98 and NT
that performs linear and nonlinear regression analysis and curve fitting.
NLREG determines the values of parameters for an equation, whose form you
specify, that cause the equation to best fit a set of data values.  NLREG
can handle linear, polynomial, exponential, logistic, periodic, and
general nonlinear functions.

NLREG features a full programming language with a syntax similar to C
for specifying the function that is to be fitted to the data. This allows
you to compute intermediate work variables, use conditionals, and even
iterate in loops.  With NLREG it is easy to construct piecewise functions
that change form over different domains.

NLREG performs true nonlinear regression, it does not transform the
function into a linear form. As a result, it can handle functions that
are impossible to linearize such as:

Y = Amplitude*SIN(Freq*X+Phase) + A*EXP(X);

Another advantage of handing the function in true nonlinear form is that
the minimization of the sum of squared residual values (i.e., "least
squares") is based on the true nonlinear value rather than some linearized
transformation.

In addition to computing the optimal values of the parameters, NLREG can
generate plots of the data points and the fitted equation. It can also
plot the distribution of residual values.

In addition to performing classic nonlinear regression, NLREG can be used
to find the root or minimum value of a general nonlinear function. It can
also be used in a special form where the independent variable is omitted;
an interesting application of this is "circular regression" where a circle
is fitted to a set of data points.

NLREG is in use at hundreds of universities, laboratories, and government
agencies around the world (including the U.S. Navy, Harvard, and Duke).
NLREG has been validated using the NIST statistical reference datasets;
the results are available on the NLREG web page.

The price of NLREG is only \$65 (\$70 if outside the USA), which is far
below the cost of comparable commercial regression programs.  And you can
download a shareware demonstration version of NLREG to try out before you
decide to purchase it.

the web site:

http://www.nlreg.com

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