I don't know if this is a bug or a missing feature, but as the following output tells, one can use the boolean expression X = 1 but not the combined expression X = 1 & Y = 2 for matrices. ? X = ones(5,1) Generated matrix X ? Y = X + 1 Generated matrix Y ? Z = (X = 1) Generated matrix Z ? Z = (X = 1 & Y = 2) Data types not conformable for operation This is on Windows XP using version 1.6.6pre1 build date 09/18/2007 If it is a missing feature, please do implement it, so that the the combined expression X = 1 & Y = 2 can be used for matrices A second bug or missing feature: I want to initiate a matrix with missing values, where some cells with missing values will later be replaced with non-missing values. I got the following result when trying to initiate a matrix with missing values: ? A = {NA, NA; NA, NA} Generated matrix A ? A A (2 x 2) 1.7977e+308 1.7977e+308 1.7977e+308 1.7977e+308 Third, I have a few feature requests: 1. It should be possible to use the xtab command with nx1 matrices, i.e. the inputs are matrix vectors 2. The xtab command should be able to take a nxn matrix with discrete values as input an calculate a cross table from this, where this matrix is the inner square matrix of the cross table (i.e. the cross table except the marginals) 3. After calculating a cross classification table from View > Cross Tabulation in the GUI, one gets the possibility to save the output table as a matrix. This feature should be available also from the command line interface. 4. The parameterts of a function can currently be of six types: bool, int, scalar, series, list, matrix. Please include a third type "discrete" or "disc" for a discrete data series 5. Create a new boolean command isdiscrete() to check if a series or matrix contains only discrete values, with outputs 1 if it is discrete and 0 otherwise. Fourth, I have a suggestion and possibly feature request: To check that a variable is discrete, accoriding to the User's Guide gretl currently checks that all values are integer multiples of 0.25 and that the variable takes on a “fairly small” set of distinct values, where “fairly small” is defined as less than or equal to 8. Would it possible to use a more exact method? For example, I use if sum(foo-int(foo))=0 discrete foo endif Best regards and thanks for a great software, Andreas