You can grow them row by row by appending or using rbind(). That does not mean you should. Dynamically growing structures is one of the least efficient ways to code in R. If you can, allocate your entire data.frame up front: N <- 1e4 # total number of rows to preallocate–possibly an overestimate DF <- … Read more
The recursive part is not quite correct. split([], [], []). split([Head|Tail], [Head|List1], List2) :- Head>=0, split(Tail, List1, List2). split([Head|Tail], List1, [Head|List2]) :- Head<0, split(Tail, List1, List2). The Head should be added to the positive list if Head >= 0 and to the negative list when Head < 0. Moreover, checking the sign of Head at … Read more
Unfortunately, there’s no easy way to do what you want. Type tests can only be used with specific types, and even if the type test passed, the conversion operator :?> also only works to cast expressions to specific types so the right hand side of your match wouldn’t do what you want anyway. You can … Read more
There is some structure to this problem, and here it comes. I’ll be using this stuff: import Control.Applicative import Data.Traversable import Data.List First up, lists-with-padding are a useful concept, so let’s have a type for them. data Padme m = (:-) {padded :: [m], padder :: m} deriving (Show, Eq) Next, I remember that the … Read more
I think you want: > do.call(rbind, lapply(my.list, data.frame, stringsAsFactors=FALSE)) global_stdev_ppb range tok global_freq_ppb 1 24267673 0.03114799 hello 211592.6 2 11561448 0.08870838 world 1002043.0 > str(do.call(rbind, lapply(my.list, data.frame, stringsAsFactors=FALSE))) ‘data.frame’: 2 obs. of 4 variables: $ global_stdev_ppb: num 24267673 11561448 $ range : num 0.0311 0.0887 $ tok : chr “hello” “world” $ global_freq_ppb : num … Read more
A logically pure implementation is very straight-forward, thanks to clpfd: :- use_module(library(clpfd)). list_evens_odds([],[],[]). list_evens_odds([X|Xs],[X|Es],Os) :- X mod 2 #= 0, list_evens_odds(Xs,Es,Os). list_evens_odds([X|Xs],Es,[X|Os]) :- X mod 2 #= 1, list_evens_odds(Xs,Es,Os). Some sample queries we expect to succeed (with a finite sequence of answers): ?- Xs = [1,2,3,4,5,6,7], list_evens_odds(Xs,Es,Os). Xs = [1,2,3,4,5,6,7], Es = [ 2, 4, … Read more
Here is another way: var chunks = []; int chunkSize = 2; for (var i = 0; i < letters.length; i += chunkSize) { chunks.add(letters.sublist(i, i+chunkSize > letters.length ? letters.length : i + chunkSize)); } return chunks; Run it on dartpad
Here’s a lazy-list Hamming numbers in Prolog using a “generator idiom”. The more I think about it the more it seems to me the lazy lists of Haskell are just open-ended (a.k.a. “difference”) lists of Prolog, and corecursion just a fancy name for the top-down list building of tail recursion modulo cons. Also, Haskell is … Read more
Maybe you want to do something like: do.call(“rbind”, my.df.list)
Assuming you actually have a List<AnObject>, all you need is list.sort(Comparator.comparing(a -> a.attr)); If you make you code clean by not using public fields, but accessor methods, it becomes even cleaner: list.sort(Comparator.comparing(AnObject::getAttr));