added predict() method for sample selection objects:  based on the code of "fg nu" posted at http://stackoverflow.com/questions/14005788/predict-function-for-heckman-model; in several cases, this function does not work; further changes are required to make this function work for all relevant cases

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/sampleselection@1566 d36ae590-6c38-44c5-9ba5-7217e93607d8
added tests for predict.selection() (in several cases, this function does not work yet)

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/sampleselection@1567 d36ae590-6c38-44c5-9ba5-7217e93607d8
updated URL to Thilo Klein's website

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/sampleselection@1568 d36ae590-6c38-44c5-9ba5-7217e93607d8
added tests for predict.selection() with Tobit-5 models estimated by the 2-step method (does not work yet)

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/sampleselection@1569 d36ae590-6c38-44c5-9ba5-7217e93607d8
Small changes in invMillsRatio() and in the examples and tests for calculating Inverse Mills Ratios for bivariate probit models so that this works with the recently released version of VGAM (0.9-4)

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/sampleselection@1570 d36ae590-6c38-44c5-9ba5-7217e93607d8
predict.selection(): added argument "part",  changed possible values of argument "type", and improved/extended the documentation

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/sampleselection@1571 d36ae590-6c38-44c5-9ba5-7217e93607d8
slightly improved formatting of this Rd file

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/sampleselection@1572 d36ae590-6c38-44c5-9ba5-7217e93607d8
in the example section in the documentation of the data set "nlswork", the commands for loading and using the "plm" package are in a "dontrun" environment now so that the sampleSelection package no longer needs to "suggest" the "plm" package

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/sampleselection@1573 d36ae590-6c38-44c5-9ba5-7217e93607d8
predict.selection() now works for 2-step estimations of Tobit-2 models; when calculating conditional expectations of the dependent variable of the outcome equation, predict.selection() now makes sure that the model matrices for the selection model and the outcome model belong to the same observations (if there are NAs in the data)

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/sampleselection@1574 d36ae590-6c38-44c5-9ba5-7217e93607d8
added several further tests for predict.selection(); removed a few obsolete tests for predict.selection()

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/sampleselection@1575 d36ae590-6c38-44c5-9ba5-7217e93607d8
slightly improved documentation of fitted.prediction()

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/sampleselection@1576 d36ae590-6c38-44c5-9ba5-7217e93607d8
predict.selection(): when providing argument "newdata", observations of the data set "newdata" with missing values are no longer removed but the returned predicted values may contain zeros

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/sampleselection@1577 d36ae590-6c38-44c5-9ba5-7217e93607d8
predict.selection() now can calculate the predicted values of the dependent variables of the two outcome equations of Tobit-5 models and returns them as a two-column matrix (not yet thoroughly tested)

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/sampleselection@1578 d36ae590-6c38-44c5-9ba5-7217e93607d8
extended and improved some tests of predict.selection()

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/sampleselection@1579 d36ae590-6c38-44c5-9ba5-7217e93607d8
corrected calculation of the predicted values of the dependent variable of the first outcome equation of Tobit-2 models

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/sampleselection@1580 d36ae590-6c38-44c5-9ba5-7217e93607d8
predict.selection(): model matrices and coefficients are now only obtained if they are needed for the specific predictions

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/sampleselection@1581 d36ae590-6c38-44c5-9ba5-7217e93607d8
predict.selection(): the matrices that are returned when predicting unconditional or conditional outputs of Tobit-5 models have column names now

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/sampleselection@1582 d36ae590-6c38-44c5-9ba5-7217e93607d8
predict.selection() no longer requires that the dependent variable(s) is (are) in the data set used as argument "newdata"

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/sampleselection@1583 d36ae590-6c38-44c5-9ba5-7217e93607d8
added tests for predict.selection() with argument "newdata" only including the variables that are necessary for calculating the respective predictions

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/sampleselection@1584 d36ae590-6c38-44c5-9ba5-7217e93607d8
predict.selection(): when predicting conditional expectations, all possible conditional expectations (i.e. both for ys=0 and ys=1) are returned

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/sampleselection@1585 d36ae590-6c38-44c5-9ba5-7217e93607d8