# Delete duplicate elements in a list from a master list [closed]

This question has been addressed adequately for pattern matching. However, I have a similar task with floating point data. I am looking for an efficient way to delete duplicates within a tolerance value (preferably a conditional statement between the elements of the two lists). Kindly help.

## closed as unclear what you're asking by Coolwater, José Antonio Díaz Navas, Henrik Schumacher, LCarvalho, MarcoBMar 2 '18 at 3:23

Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

• to get fast answer, you need to provide a MWE. – Nasser Feb 28 '18 at 11:09
• Hi, please read asking guidelines. Your question is missing an input example as well as examples of your attempts. Have you seen DeleteDuplicates/DeleteDuplicatesBy? – Kuba Feb 28 '18 at 11:09

master = RandomReal[{0, 1}, 1000];
sub = RandomReal[{0, 1}, 100];

{roundm, rounds} = Round[{master, sub}, 0.01];

s2 = DeleteDuplicates[Join[roundm, {Null}, rounds]] /. {a__, Null, b___} :> {b};

sub2 = Extract[sub, Flatten[Position[rounds, #] & /@ s2, 1]]


sub2 contains all the reals in sub that do not match master within the tolerance specified in Round.

For a faster version use makePositionFunction in the last step.

makePositionFunction[f_Symbol, data_, level_: {-1}] := Block[{},
ClearAll[f];
Reap[
MapIndexed[Sow[#2, #1] &, data, level, Heads -> True],
_, (f[#] = #2) &];
f[other_] := Position[data, other, level]]

makePositionFunction[pos, rounds];

sub2 = Extract[sub, Flatten[pos /@ s2, 1]]

SeedRandom[1]
ClearAll[list, masterlist]
{list, masterlist} = Round[RandomReal[1, {2, 10}], 0.01];
tolerance = .02;

dist = Nearest[masterlist->"Distance"];

Pick[list, dist[#][[1]]>tolerance & /@ list] (* or *)
Pick[list, UnitStep[dist[#][[1]] & /@ list - tolerance], 1]


{0.11, 0.79, 0.07, 0.54, 0.7}

dist0 = Nearest[masterlist -> {"Element", "Distance"}];
res = {#, dist0[#][[1]]} & /@ list;

Grid[Prepend[If[#[[2, -1]] > tolerance, Flatten@Map[Style[#, Red, Bold] &, #, {-1}],
Flatten@#] & /@ res,
{Column[{"element in", "list"}, Alignment -> Center],
Column[{"Nearest" , "element in", "masterlist"}, Alignment -> Center], "distance"}],
Dividers -> All, Alignment -> {Center, Center}]