/* strcmp95.c Version 2 */ /* The strcmp95 function returns a double precision value from 0.0 (total disagreement) to 1.0 (character-by-character agreement). The returned value is a measure of the similarity of the two strings. */ /* Date of Release: Jan. 26, 1994 */ /* Modified: April 24, 1994 Corrected the processing of the single length character strings. Authors: This function was written using the logic from code written by Bill Winkler, George McLaughlin and Matt Jaro with modifications by Maureen Lynch. Comment: This is the official string comparator to be used for matching during the 1995 Test Census. */ #include #include #define NOTNUM(c) ((c>57) || (c<48)) #define INRANGE(c) ((c>0) && (c<91)) #define MAX_VAR_SIZE 61 #define NULL60 " " double strcmp95(char *ying, char *yang, long y_length, int *ind_c) { /* Arguments: ying and yang are pointers to the 2 strings to be compared. The strings need not be NUL-terminated strings because the length is passed. y_length is the length of the strings. ind_c is an array that is used to define whether certain options should be activated. A nonzero value indicates the option is deactivated. The options are: ind_c[0] Increase the probability of a match when the number of matched characters is large. This option allows for a little more tolerance when the strings are large. It is not an appropriate test when comparing fixed length fields such as phone and social security numbers. ind_c[1] All lower case characters are converted to upper case prior to the comparison. Disabling this feature means that the lower case string "code" will not be recognized as the same as the upper case string "CODE". Also, the adjustment for similar characters section only applies to uppercase characters. The suggested values are all zeros for character strings such as names. */ static int pass=1/* TODO: make it an option parameter */, adjwt[91][91]; static char sp[39][2] = {'A','E', 'A','I', 'A','O', 'A','U', 'B','V', 'E','I', 'E','O', 'E','U', 'I','O', 'I','U', 'O','U', 'I','Y', 'E','Y', 'C','G', 'E','F', 'W','U', 'W','V', 'X','K', 'S','Z', 'X','S', 'Q','C', 'U','V', 'M','N', 'L','I', 'Q','O', 'P','R', 'I','J', '2','Z', '5','S', '8','B', '1','I', '1','L', '0','O', '0','Q', 'C','K', 'G','J', 'E',' ', 'Y',' ', 'S',' '}; char ying_hold[MAX_VAR_SIZE], yang_hold[MAX_VAR_SIZE], ying_flag[MAX_VAR_SIZE], yang_flag[MAX_VAR_SIZE]; double weight, Num_sim; long minv, search_range, lowlim, ying_length, hilim, N_trans, Num_com, yang_length; int yl1, yi_st, N_simi; register int i, j, k; /* Initialize the adjwt array on the first call to the function only. The adjwt array is used to give partial credit for characters that may be errors due to known phonetic or character recognition errors. A typical example is to match the letter "O" with the number "0" */ if (!pass) { pass++; for (i=0; i<91; i++) for (j=0; j<91; j++) adjwt[i][j] = 0; for (i=0; i<36; i++) { adjwt[sp[i][0]][sp[i][1]] = 3; adjwt[sp[i][1]][sp[i][0]] = 3; } } /* If either string is blank - return - added in Version 2 */ if (!strncmp(ying,NULL60,y_length)) return(0.0); if (!strncmp(yang,NULL60,y_length)) return(0.0); /* Identify the strings to be compared by stripping off all leading and trailing spaces. */ k = y_length - 1; for(j = 0;((ying[j]==' ') && (j < k));j++); for(i = k;((ying[i]==' ') && (i > 0));i--); ying_length = i + 1 - j; yi_st = j; for(j = 0;((yang[j]==' ') && (j < k));j++); for(i = k;((yang[i]==' ') && (i > 0));i--); yang_length = i + 1 - j; ying_hold[0]=yang_hold[0]=0; strncat(ying_hold,&ying[yi_st],ying_length); strncat(yang_hold,&yang[j],yang_length); if (ying_length > yang_length) { search_range = ying_length; minv = yang_length; } else { search_range = yang_length; minv = ying_length; } /* If either string is blank - return */ /* if (!minv) return(0.0); removed in version 2 */ /* Blank out the flags */ ying_flag[0] = yang_flag[0] = 0; strncat(ying_flag,NULL60,search_range); strncat(yang_flag,NULL60,search_range); search_range = (search_range/2) - 1; if (search_range < 0) search_range = 0; /* added in version 2 */ /* Convert all lower case characters to upper case. */ if (!ind_c[1]) { for (i = 0;i < ying_length;i++) if (islower(ying_hold[i])) ying_hold[i] -= 32; for (j = 0;j < yang_length;j++) if (islower(yang_hold[j])) yang_hold[j] -= 32; } /* Looking only within the search range, count and flag the matched pairs. */ Num_com = 0; yl1 = yang_length - 1; for (i = 0;i < ying_length;i++) { lowlim = (i >= search_range) ? i - search_range : 0; hilim = ((i + search_range) <= yl1) ? (i + search_range) : yl1; for (j = lowlim;j <= hilim;j++) { if ((yang_flag[j] != '1') && (yang_hold[j] == ying_hold[i])) { yang_flag[j] = '1'; ying_flag[i] = '1'; Num_com++; break; } } } /* If no characters in common - return */ if (!Num_com) return(0.0); /* Count the number of transpositions */ k = N_trans = 0; for (i = 0;i < ying_length;i++) { if (ying_flag[i] == '1') { for (j = k;j < yang_length;j++) { if (yang_flag[j] == '1') { k = j + 1; break; } } if (ying_hold[i] != yang_hold[j]) N_trans++; } } N_trans = N_trans / 2; /* adjust for similarities in nonmatched characters */ N_simi = 0; if (minv > Num_com) { for (i = 0;i < ying_length;i++) { if (ying_flag[i] == ' ' && INRANGE(ying_hold[i])) { for (j = 0;j < yang_length;j++) { if (yang_flag[j] == ' ' && INRANGE(yang_hold[j])) { if (adjwt[ying_hold[i]][yang_hold[j]] > 0) { N_simi += adjwt[ying_hold[i]][yang_hold[j]]; yang_flag[j] = '2'; break; } } } } } } Num_sim = ((double) N_simi)/10.0 + Num_com; /* Main weight computation. */ weight= Num_sim / ((double) ying_length) + Num_sim / ((double) yang_length) + ((double) (Num_com - N_trans)) / ((double) Num_com); weight = weight / 3.0; /* Continue to boost the weight if the strings are similar */ if (weight > 0.7) { /* Adjust for having up to the first 4 characters in common */ j = (minv >= 4) ? 4 : minv; for (i=0;((i .5 of remaining characters. */ if ((!ind_c[0]) && (minv>4) && (Num_com>i+1) && (2*Num_com>=minv+i)) if (NOTNUM(ying_hold[0])) weight += (double) (1.0-weight) * ((double) (Num_com-i-1) / ((double) (ying_length+yang_length-i*2+2))); } return(weight); } /* strcmp95 */