The toolbox regtools provides three functions for performing linear and non linear regression analysis.
linregr() provides an interactive user interface for linear regression analysis, including plot facilities and the most relevant statistical information at the solution.
nlinregr() provides an interactive user interface for performing non linear (weighted) regression analysis. Plot facilities and statistical information are available.
Both functions can be called in silent command line mode.
nlinlsq() is a more flexible non linear (weighted) regression analysis function - called by nlinregr(). nlinlsq() uses the scilab function optim() for solving the regression problem and supports both analytical and numerical derivatives. Consider using R for difficult problems (http://www.r-project.org/).
A function qqplot() is also included - providing quantile-quantile plots.
Version 0.3 fix some bugs in linregr() related to confidence intervals.