Hello,
I’m searching a proc in sas to find the K nearest neighbors in a set of points.
In the following data step, I generate a random set of 100 observations.
DATA observations;
do ID=1 TO 100;
x1 = RAND('NORMAL',0,1);
x2 = RAND('NORMAL',0,1);
x3 = RAND('NORMAL',0,1);
output;
end;
run;
For example, with this set of 100 observations, is there a proc to search the 10 nearest neighbor (Euclidian distance) of the point [ 0.5 ; 0.5 ; 0.5 ]?
Please note that I already found proc discrim to apply a KNN classification. But I want the list of the K nearest neighbor and not to make a classification.
Thx!
Why not just code it yourself?
data observations;
do ID=1 TO 100;
x1 = RAND('NORMAL',0,1);
x2 = RAND('NORMAL',0,1);
x3 = RAND('NORMAL',0,1);
output;
end;
run;
proc sql noprint ;
create table distance as
select distinct id,x1,x2,x3,sqrt((x1-y1)**2 + (x2-y2)**2 + (x3-y3)**2) as distance
from observations
, (select 0.5 as y1,0.5 as y2, 0.5 as y3 from observations(obs=1) )
order by distance desc
;
quit;
data top10;
set distance (obs=10);
run;
proc print; run;
One quick way to find nearest neighbors in a large set of observations is PROC MODECLUS. Your specific problem could be solved by:
DATA observations;
do ID=1 TO 100;
x1 = RAND('NORMAL',0,1);
x2 = RAND('NORMAL',0,1);
x3 = RAND('NORMAL',0,1);
output;
end;
run;DATA position;
ID = -999;
x1 = 0.5;
x2 = 0.5;
x3 = 0.5;
run;proc sql;
create table test as
(select * from position)
union all
(select * from observations)
order by ID;ods _all_ close;
proc modeclus data=test dk=11 /* = 10 observations + 1 position */ neighbor;
var x1 x2 x3;
id ID;
ods output Neighbor=nTest;
run;ods listing;
proc sql inobs=10;
select nBor as ID, distance from nTest;
Hello Tom & PGStats,
many thanks for your help !
based on the message from Tom, I have buil the following macro "listOfKNN":
data observations;
do ID=1 TO 100000;
x1 = RAND('NORMAL',0,1);
x2 = RAND('NORMAL',0,1);
x3 = RAND('NORMAL',0,1);
output;
end;
run;
%macro listOfKNN (obser , target, K, nameOutput);
%Let dim = %eval(%SYSFUNC(count(&target,%NRSTR( )))+1) ;
%let ttt =;
%DO ii = 1 %TO &dim;
%let ttt = &ttt.(x&ii.-%scan(&target,&ii," "))**2;
%IF &ii NE &dim %THEN
%let ttt = &ttt.+;
%END;
proc sql noprint ;
create table &nameOutput as
select distinct *, sqrt(&ttt)as distance
from &obser
order by distance;
quit;
data &nameOutput;
set &nameOutput (obs=&K);
drop distance;
run;
%mend listOfKNN;
/*make a test*/
%listOfKNN( obser = observations,
target = 0.5 1 1,
K = 5,
nameOutput = out
);
B.R.
Olivier
Don't miss out on SAS Innovate - Register now for the FREE Livestream!
Can't make it to Vegas? No problem! Watch our general sessions LIVE or on-demand starting April 17th. Hear from SAS execs, best-selling author Adam Grant, Hot Ones host Sean Evans, top tech journalist Kara Swisher, AI expert Cassie Kozyrkov, and the mind-blowing dance crew iLuminate! Plus, get access to over 20 breakout sessions.
ANOVA, or Analysis Of Variance, is used to compare the averages or means of two or more populations to better understand how they differ. Watch this tutorial for more.
Find more tutorials on the SAS Users YouTube channel.