To give your task a name: You’re looking for the relative complement aka set difference between two arrays: In set-theory notation, it would be $ItemArray \ $ExclusionArray, i.e., those elements in $ItemArray that aren’t also in $ExclusionArray. This related question is looking for the symmetric difference between two sets, i.e., the set of elements that … Read more
sqldf provides a nice solution a1 <- data.frame(a = 1:5, b=letters[1:5]) a2 <- data.frame(a = 1:3, b=letters[1:3]) require(sqldf) a1NotIna2 <- sqldf(‘SELECT * FROM a1 EXCEPT SELECT * FROM a2’) And the rows which are in both data frames: a1Ina2 <- sqldf(‘SELECT * FROM a1 INTERSECT SELECT * FROM a2’) The new version of dplyr has … Read more
To get elements which are in temp1 but not in temp2 (assuming uniqueness of the elements in each list): In [5]: list(set(temp1) – set(temp2)) Out[5]: [‘Four’, ‘Three’] Beware that it is asymmetric : In [5]: set([1, 2]) – set([2, 3]) Out[5]: set([1]) where you might expect/want it to equal set([1, 3]). If you do want set([1, 3]) … Read more
You could define three functions inBoth, inFirstOnly, and inSecondOnly which all take two lists as arguments, and return a list as can be understood from the function name. The main logic could be put in a common function operation that all three rely on. Here are a few implementations for that operation to choose from, … Read more
It really depends on your regex flavor. .NET … provides only one simple character class set operation: subtraction. This is enough for your example, so you can simply use [\w-[_]] If a – is followed by a nested character class, it’s subtracted. Simple as that… Java … provides a much richer set of character class … Read more
if don’t know if this is most effective, but perhaps the shortest A = [1, 2, 3, 4]; B = [1, 3, 4, 7]; diff = A.filter(function(x) { return B.indexOf(x) < 0 }) console.log(diff); Updated to ES6: A = [1, 2, 3, 4]; B = [1, 3, 4, 7]; diff = A.filter(x => !B.includes(x) ); … Read more
Get difference between two lists