Question

我在Matlab中有一个字符串，想要用另一个模式替换其中某些模式的第三个外观。我怎么能这样做？

例如：

str = 'ter-yu-ter-u-ter-hg';
patternRemove = 'ter';
patternAdd = 'mov';

答案：

str = 'ter-yu-ter-u-mov-hg';

Answer 1

抱歉，我无法为您提供更多帮助，但我不知道您是如何在Matlab中进行的。如果我试图解决这个问题，我就是这样做的。

<?php

$i = 0; // SET A DEFAULT VALUE FOR OUR COUNTER
$str = 'ter-yu-ter-u-ter-hg-ter-as-b-ter-a-sdf-w-ter-s-ter-asd'; // TEXT TO WORK ON
$remove = 'ter'; // TEXT TO REPLACE EACH THIRD OCCURRENCE OF 
$replace = 'mov'; // TEXT TO REPLACE EACH THIRD OCCURRENCE WITH

// USE A CALLBACK FUNCTION TO CHECK TO SEE HOW MANY TIMES IT'S FOUND A MATCH
// INCREMENT THE COUNTER EACH TIME
// IF THE COUNTER IS 3, RESET IT TO ZERO AND MAKE THE REPLACEMENT
$string = preg_replace_callback('/'.$remove.'/', function($m) use(&$i, $remove, $replace) {$a = $remove; if (++$i == 3) {$i = 0; $a = $replace;} return $a;}, $str);

print $string;

这输出以下内容：

ter-yu-ter-u-mov-hg-ter-as-b-ter-a-sdf-w-mov-s-ter-asd

如果您没有与preg_replace_callback类似的功能，则可能会在搜索字词中将其分成多个段，并在remove处分开。然后遍历所有字符串部分并每次递增计数器。如果计数器除以3的余数为零，则应用替换。

以下是使用foreach：

的示例

// SET THE DEFAULTS
$i = 0;
$str = 'ter-yu-ter-u-ter-hg-ter-as-b-ter-a-sdf-w-ter-s-ter-asd';
$remove = 'ter';
$replace = 'mov';
$final_string = ''; // THIS WILL BE OUR OUTPUT STRING LATER

// BREAK APART THE STRING INTO AN ARRAY OF MATCHES, BASED ON THE $remove VALUE
$matches_for_remove = explode($remove, $str);

// LOOP THROUGH EACH ITEM IN THE ARRAY
foreach ($matches_for_remove AS $match) {

    // SET THE DEFAULT STRING TO $remove
    $replacement_string = $remove;
    if (++$i % 3 == 0) { // IF THE REMAINDER IS ZERO, THEN DO THE REPLACEMENT
        $replacement_string = $replace; 
    }

    // IF IT'S NOT THE END, APPEND THE remove OR replace PORTION ON TO THE END
    if ($i == count($matches_for_remove)){
        $final_string .= $match;
    }
    else {
        $final_string .= $match.$replacement_string;
    }

}

print $final_string;

同样的示例，但使用for循环而不是foreach：

$str = 'ter-yu-ter-u-ter-hg-ter-as-b-ter-a-sdf-w-ter-s-ter-asd';
$remove = 'ter';
$replace = 'mov';
$final_string = '';

for ($i = 0; $i < count($matches_for_remove); $i++) {

    $replacement_string = $remove;

    if (($i + 1) % 3 == 0) {
        $replacement_string = $replace;
    }

    if ($i == count($matches_for_remove) - 1) {
        $final_string .= $matches_for_remove[$i];
    }
    else {
        $final_string .= $matches_for_remove[$i].$replacement_string;
    }

}

print $final_string;

再次，抱歉，如果我用PHP编写的例子没有任何意义。我理解这个概念，而不是如何将其转化为Matlab。但是，希望这至少会让你指出正确的方向。

Answer 2

str = 'ter-yu-ter-u-ter-hg';
patternRemove = 'ter';
patternAdd = 'mov';

ind = regexp(str,patternRemove);
ii = ind(3);
strOut = [str(1:ii-1) patternAdd str(ii+numel(patternRemove):end)];

在regexprep中选择模式

2 个答案: