[Gretl-devel] Making the programming of user defined functions easier

To make the programming of user defined functions easier, I would like to have access to the following new commands in gretl: 1. sampleranks() or tiedranks() or rankorder(): A function taking as input one or two data series or matrix vectors and returning a series or matrix vector with the sample ranks of the values in these, from smallest to largest, with ties, i.e., equal values, resulting in ranks being averaged. For example sampleranks(x) would rank the observations from variable x only, while sampleranks(x,y) would rank the observations from both variables jointly. 2. floor(): Round down to nearest integer. A complement to the current commands ceil(), that round up to nearest integer. As int() gives just the integer part, it gives the same value as floor() for positive values but the values for ceil() for negative values, thus floor() is needed for obtaining a round down to nearest integer for negative values. And floor() is a standrad matematical function that shouldn't be absent from gretl. 3. factorial(): Taking a nonnegative integer as input, with factorial(n) = n! Of course one can use gammafunc(n+1) instead, but factorial(n) would be more intuitive. 4. permutation(): Taking two nonnegative integers as input, with permutation(n,x) = n!/(n-x)!, i.e., the number of possible arrangements when x objects are to be selected from a total of n and arranged in order. Of course one can use gammafunc(n+1)/gammafunc(n-x+1) instead, but permutation(n,x) is easier and more intuitive. 4. combination(): Taking two nonnegative integers as input, with combination(n,x) = n!/x!(n-x)!, i.e., the number of possible selections when x objects are to be selected from a total of n and order is not of importance. Of course one can use gammafunc(n+1)/gammafunc(x+1)*gammafunc(n-x+1) instead, but combination(n,x) is easier and more intuitive. Best regards Andreas