;+ ; NAME: ; MATCH2 ; PURPOSE: ; Routine to cross-match values in two vectors (including non-matches) ; EXPLANATION: ; MATCH2 reports matching elements of two arrays. ; This procedure *appears* similar to MATCH of the IDL astronomy ; library. However, this routine is quite different in that it ; reports an index value for each element of the input arrays. ; In other words, while MATCH reports the *existence* of ; matching elements in each array, MATCH2 reports explicitly ; *which* elements match. ; ; Furthermore, while MATCH reports only unique matching ; elements, MATCH2 will always report a cross-match for every ; element in each array, even if it is a repeat. ; ; In cases where no match was found, an index of -1 is ; reported. ; ; CALLING SEQUENCE: ; match2, a, b, suba, subb ; ; INPUTS: ; a,b - two vectors to match elements, numeric or string data ; types. (See below for RESTRICTIONS on A and B) ; ; ; OUTPUTS: ; suba - vector with same number of elements as A, such that ; A EQ B[SUBA], except non-matches which are indicated ; by SUBA EQ -1 ; subb - vector with same number of elements as B, such that ; B EQ A[SUBB], except non-matches which are indicated ; by SUBB EQ -1 ; ; ; RESTRICTIONS: ; ; The vectors A and B are allowed to have duplicates in them, ; but for matching purposes, only the first one found will ; be reported. ; ; MATCH2 internally converts values to double precision and so ; cannot be used with long64 integers that cannot be converted to double. ; Best to convert such long64 integers to strings before matching. ; ; If A and B are string arrays, then non-printable ASCII values ; 1B and 2B will confuse the algorithm. Don't use these ; non-printable characters in strings. ; ; EXAMPLE: ; A = [0,7,14,23,24,30] ; B = [7,8,14,25,14] ; IDL> match2, a, b, suba, subb ; --> suba = [ -1 , 0, 4, -1, -1, -1 ] ; (indicates that A[1] matches B[1] and A[3] matches B[2]) ; --> subb = [ 1 , -1, 2, -1, 2 ] ; (indicates that B[1] matches A[1] and B[2] matches A[3]) ; ; Compare to the results of the original MATCH procedure, ; ; IDL> match, a, b, suba, subb ; --> suba = [ 1, 3] ; (indicates that A[1] and A[3] match elements in B, but not which ones) ; --> subb = [ 1, 2] ; (indicates that B[1] and B[2] match elements in A, but not which ones) ; ; MODIFICATION HISTORY ; Derived from the IDL Astronomy Library MATCH, 14 Feb 2007 ; Updated documentation, 17 Jul 2007 ; More updated documentation (example), 03 Sep 2007 ; Bug fix for string arrays with numerical contents; the subset ; string is now 1B and 2B; this is now documented, 2014-10-20 CM ; Added warning about problems with LONG64 values WL 2020-10-29 ; ; ;- ;------------------------------------------------------------------------- pro match2, a, b, suba, subb On_error,2 compile_opt idl2 if N_params() LT 3 then begin print,'Syntax - match2, a, b, suba, subb' print,' a,b -- input vectors for which to match elements' print,' suba,subb -- match index lists' return endif da = size(a,/type) & db =size(b,/type) na = N_elements(a) ;number of elements in a nb = N_elements(b) ;number of elements in b suba = lonarr(na)-1 & subb = lonarr(nb)-1 ; Check for a single element array if (na EQ 1) or (nb EQ 1) then begin if (nb GT 1) then begin wh = where(b EQ a[0], nw) if nw GT 0 then begin subb[wh] = 0L suba[0] = wh[0] endif endif else begin wh = where(a EQ b[0], nw) if nw GT 0 then begin suba[wh] = 0L subb[0] = wh[0] endif endelse return endif c = [ a, b ] ;combined list of a and b ind = [ lindgen(na), lindgen(nb) ] ;combined list of indices vec = [ intarr(na), replicate(1,nb) ] ;flag of which vector in combined ;list 0 - a 1 - b ; sort combined list if da EQ 7 OR db EQ 7 then begin ;String input? vecstr = [string(1b), string(2b)] ;; String sort (w/ double key) sub = sort(c+vecstr[vec]) endif else begin ;; Number sort (w/ double key) mc = machar(/double) if (da ge 12) || (db ge 12) && (max(c) gt (long64(mc.ibeta))^(mc.it)) then message, \$ 'ERROR - match2 cannot be used with values exceeding double precision range. sub = sort(double(c)*(1d + vec*mc.eps)) endelse c = c[sub] ind = ind[sub] vec = vec[sub] n = na + nb ;total elements in c wh = where( c[1:*] NE c, ct) if ct EQ 0 then begin whfirst = [0] whlast = [n-1] endif else begin whfirst = [0, wh+1] whlast = [wh, n-1] endelse vec0 = vec[whfirst] vec1 = vec[whlast] ;; 0 = present in A but not B ;; 1 = can't occur (since the array was sorted on 'VEC') ;; 2 = present in both ;; 3 = present in B but not A matchtype = vec0 + vec1*2 nm = n_elements(matchtype) mm = ind*0L & wa = mm & wb = mm for i = 0, nm-1 do begin mm[whfirst[i]:whlast[i]] = matchtype[i] wa[whfirst[i]:whlast[i]] = ind[whfirst[i]] wb[whfirst[i]:whlast[i]] = ind[whlast[i]] endfor suba = lonarr(na)-1 & subb = lonarr(nb)-1 wh = where(mm EQ 2 AND vec EQ 0, ct) if ct GT 0 then suba[ind[wh]] = wb[wh] wh = where(mm EQ 2 AND vec EQ 1, ct) if ct GT 0 then subb[ind[wh]] = wa[wh] return end