similar_text如何工作？(How does similar_text work?)
我刚刚发现了Similar_text功能，并且正在玩弄，但输出的百分比总是让我感到惊讶。 参见下面的例子。
我试图找到关于PHP所提及的算法的信息：
similar_text()文档 ：<?php $p = 0; similar_text('aaaaaaaaaa', 'aaaaa', $p); echo $p . "<hr>"; //66.666666666667 //Since 5 out of 10 chars match, I would expect a 50% match similar_text('aaaaaaaaaaaaaaaaaaaa', 'aaaaa', $p); echo $p . "<hr>"; //40 //5 out of 20 > not 25% ? similar_text('aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa', 'aaaaa', $p); echo $p . "<hr>"; //9.5238095238095 //5 out of 100 > not 5% ? //Example from PHP.net //Why is turning the strings around changing the result? similar_text('PHP IS GREAT', 'WITH MYSQL', $p); echo $p . "<hr>"; //27.272727272727 similar_text('WITH MYSQL', 'PHP IS GREAT', $p); echo $p . "<hr>"; //18.181818181818 ?>任何人都可以解释这是如何实际工作的？
更新：
感谢我的意见，我发现百分比实际上是使用类似的特征数* 200 / length1 + lenght 2
Z_DVAL_PP(percent) = sim * 200.0 / (t1_len + t2_len);所以这就解释了为什么percenatges高于预期。 有一个字符串与95中的5个结果是10，所以我可以使用。
similar_text('aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa', 'aaaaa', $p); echo $p . "<hr>"; //10 //5 out of 95 = 5 * 200 / (5 + 95) = 10但是我仍然不明白为什么PHP在转动字符串时返回不同的结果。 dfsq提供的JS代码不会这样做。 看看PHP中的源代码，我只能在以下行找到一个区别，但是我不是ac程序员。 一些洞察有什么区别，不胜感激。
在JS中
for (l = 0;(p + l < firstLength) && (q + l < secondLength) && (first.charAt(p + l) === second.charAt(q + l)); l++);在PHP中：（php_similar_str函数）
for (l = 0; (p + l < end1) && (q + l < end2) && (p[l] == q[l]); l++);资源：
/* {{{ proto int similar_text(string str1, string str2 [, float percent]) Calculates the similarity between two strings */ PHP_FUNCTION(similar_text) { char *t1, *t2; zval **percent = NULL; int ac = ZEND_NUM_ARGS(); int sim; int t1_len, t2_len; if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "ss|Z", &t1, &t1_len, &t2, &t2_len, &percent) == FAILURE) { return; } if (ac > 2) { convert_to_double_ex(percent); } if (t1_len + t2_len == 0) { if (ac > 2) { Z_DVAL_PP(percent) = 0; } RETURN_LONG(0); } sim = php_similar_char(t1, t1_len, t2, t2_len); if (ac > 2) { Z_DVAL_PP(percent) = sim * 200.0 / (t1_len + t2_len); } RETURN_LONG(sim); } /* }}} */ /* {{{ php_similar_str */ static void php_similar_str(const char *txt1, int len1, const char *txt2, int len2, int *pos1, int *pos2, int *max) { char *p, *q; char *end1 = (char *) txt1 + len1; char *end2 = (char *) txt2 + len2; int l; *max = 0; for (p = (char *) txt1; p < end1; p++) { for (q = (char *) txt2; q < end2; q++) { for (l = 0; (p + l < end1) && (q + l < end2) && (p[l] == q[l]); l++); if (l > *max) { *max = l; *pos1 = p - txt1; *pos2 = q - txt2; } } } } /* }}} */ /* {{{ php_similar_char */ static int php_similar_char(const char *txt1, int len1, const char *txt2, int len2) { int sum; int pos1, pos2, max; php_similar_str(txt1, len1, txt2, len2, &pos1, &pos2, &max); if ((sum = max)) { if (pos1 && pos2) { sum += php_similar_char(txt1, pos1, txt2, pos2); } if ((pos1 + max < len1) && (pos2 + max < len2)) { sum += php_similar_char(txt1 + pos1 + max, len1 - pos1 - max, txt2 + pos2 + max, len2 - pos2 - max); } } return sum; } /* }}} */源码在Javascript中： 类似的文本端口到javascript
I just found the similar_text function and was playing around with it, but the percentage output always suprises me. See the examples below.
I tried to find information on the algorithm used as mentioned on php:
similar_text()Docs:<?php $p = 0; similar_text('aaaaaaaaaa', 'aaaaa', $p); echo $p . "<hr>"; //66.666666666667 //Since 5 out of 10 chars match, I would expect a 50% match similar_text('aaaaaaaaaaaaaaaaaaaa', 'aaaaa', $p); echo $p . "<hr>"; //40 //5 out of 20 > not 25% ? similar_text('aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa', 'aaaaa', $p); echo $p . "<hr>"; //9.5238095238095 //5 out of 100 > not 5% ? //Example from PHP.net //Why is turning the strings around changing the result? similar_text('PHP IS GREAT', 'WITH MYSQL', $p); echo $p . "<hr>"; //27.272727272727 similar_text('WITH MYSQL', 'PHP IS GREAT', $p); echo $p . "<hr>"; //18.181818181818 ?>Can anybody explain how this actually works?
Update:
Thanks to the comments I found that the percentage is actually calculated using the number of similar charactors * 200 / length1 + lenght 2
Z_DVAL_PP(percent) = sim * 200.0 / (t1_len + t2_len);So that explains why the percenatges are higher then expected. With a string with 5 out of 95 it turns out 10, so that I can use.
similar_text('aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa', 'aaaaa', $p); echo $p . "<hr>"; //10 //5 out of 95 = 5 * 200 / (5 + 95) = 10But I still cant figure out why PHP returns a different result on turning the strings around. The JS code provided by dfsq doesn't do this. Looking at the source code in PHP I can only find a difference in the following line, but i'm not a c programmer. Some insight in what the difference is, would be appreciated.
In JS:
for (l = 0;(p + l < firstLength) && (q + l < secondLength) && (first.charAt(p + l) === second.charAt(q + l)); l++);In PHP: (php_similar_str function)
for (l = 0; (p + l < end1) && (q + l < end2) && (p[l] == q[l]); l++);Source:
/* {{{ proto int similar_text(string str1, string str2 [, float percent]) Calculates the similarity between two strings */ PHP_FUNCTION(similar_text) { char *t1, *t2; zval **percent = NULL; int ac = ZEND_NUM_ARGS(); int sim; int t1_len, t2_len; if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "ss|Z", &t1, &t1_len, &t2, &t2_len, &percent) == FAILURE) { return; } if (ac > 2) { convert_to_double_ex(percent); } if (t1_len + t2_len == 0) { if (ac > 2) { Z_DVAL_PP(percent) = 0; } RETURN_LONG(0); } sim = php_similar_char(t1, t1_len, t2, t2_len); if (ac > 2) { Z_DVAL_PP(percent) = sim * 200.0 / (t1_len + t2_len); } RETURN_LONG(sim); } /* }}} */ /* {{{ php_similar_str */ static void php_similar_str(const char *txt1, int len1, const char *txt2, int len2, int *pos1, int *pos2, int *max) { char *p, *q; char *end1 = (char *) txt1 + len1; char *end2 = (char *) txt2 + len2; int l; *max = 0; for (p = (char *) txt1; p < end1; p++) { for (q = (char *) txt2; q < end2; q++) { for (l = 0; (p + l < end1) && (q + l < end2) && (p[l] == q[l]); l++); if (l > *max) { *max = l; *pos1 = p - txt1; *pos2 = q - txt2; } } } } /* }}} */ /* {{{ php_similar_char */ static int php_similar_char(const char *txt1, int len1, const char *txt2, int len2) { int sum; int pos1, pos2, max; php_similar_str(txt1, len1, txt2, len2, &pos1, &pos2, &max); if ((sum = max)) { if (pos1 && pos2) { sum += php_similar_char(txt1, pos1, txt2, pos2); } if ((pos1 + max < len1) && (pos2 + max < len2)) { sum += php_similar_char(txt1 + pos1 + max, len1 - pos1 - max, txt2 + pos2 + max, len2 - pos2 - max); } } return sum; } /* }}} */Source in Javascript: similar text port to javascript
原文：https://stackoverflow.com/questions/14136349
更新时间：2022-03-06 06:03
最满意答案
要么你作为一个矩阵使用它：
holder<-matrix(0,nrow=3,ncol=3) for(i in 1:3){ apple<-c(i+1, i*2, i^3) holder[,i]<-apple # columnwise, that's how sapply does it too }或者您使用列表：
holder <- vector('list',3) for(i in 1:3){ apple<-c(i+1, i*2, i^3) holder[[i]]<-apple }或者你只是做R方式：
holder <- sapply(1:3,function(i) c(i+1, i*2,i^3)) holder.list <- sapply(1:3,function(i) c(i+1, i*2,i^3),simplify=FALSE)旁注：如果你在R中遇到这个非常基本的问题，我强烈建议你浏览一下你在网上找到的任何介绍。 你得到一个列表：
either you work with it as a matrix :
holder<-matrix(0,nrow=3,ncol=3) for(i in 1:3){ apple<-c(i+1, i*2, i^3) holder[,i]<-apple # columnwise, that's how sapply does it too }Or you use lists:
holder <- vector('list',3) for(i in 1:3){ apple<-c(i+1, i*2, i^3) holder[[i]]<-apple }Or you just do it the R way :
holder <- sapply(1:3,function(i) c(i+1, i*2,i^3)) holder.list <- sapply(1:3,function(i) c(i+1, i*2,i^3),simplify=FALSE)On a sidenote : if you struggle with this very basic problem in R, I strongly recommend you to browse through any of the introductions you find on the web. You get a list of them at :
Where can I find useful R tutorials with various implementations?
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