blocks|key|470009|text|我将看一下ifelse命令。我会说它更好，因为它也是矢量化的。使用汽车数据集的示例：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|470010|>+cars$speed+>+20
+[1]+FALSE+FALSE+FALSE+FALSE+FALSE+FALSE+FALSE+FALSE+FALSE+FALSE+FALSE+FALSE
[13]+FALSE+FALSE+FALSE+FALSE+FALSE+FALSE+FALSE+FALSE+FALSE+FALSE+FALSE+FALSE
[25]+FALSE+FALSE+FALSE+FALSE+FALSE+FALSE+FALSE+FALSE+FALSE+FALSE+FALSE+FALSE
[37]+FALSE+FALSE+FALSE+FALSE+FALSE+FALSE+FALSE++TRUE++TRUE++TRUE++TRUE++TRUE
[49]++TRUE++TRUE

>+ifelse(cars$speed+>+20,+'fast',+'slow')
+[1]+"slow"+"slow"+"slow"+"slow"+"slow"+"slow"+"slow"+"slow"+"slow"+"slow"
[11]+"slow"+"slow"+"slow"+"slow"+"slow"+"slow"+"slow"+"slow"+"slow"+"slow"
[21]+"slow"+"slow"+"slow"+"slow"+"slow"+"slow"+"slow"+"slow"+"slow"+"slow"
[31]+"slow"+"slow"+"slow"+"slow"+"slow"+"slow"+"slow"+"slow"+"slow"+"slow"
[41]+"slow"+"slow"+"slow"+"fast"+"fast"+"fast"+"fast"+"fast"+"fast"+"fast"|code-block|syntax|javascript|470011|entityMap^0|5|6|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|P|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Q|8|@]|D|@]|E|$]]]|L|$]]

I would take a look at the <code>ifelse</code> command. I would call it even better because it is also vectorized. An example using the cars dataset:

<pre><code>&gt; cars$speed &gt; 20
 [1] FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE
[13] FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE
[25] FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE
[37] FALSE FALSE FALSE FALSE FALSE FALSE FALSE TRUE TRUE TRUE TRUE TRUE
[49] TRUE TRUE

&gt; ifelse(cars$speed &gt; 20, 'fast', 'slow')
 [1] "slow" "slow" "slow" "slow" "slow" "slow" "slow" "slow" "slow" "slow"
[11] "slow" "slow" "slow" "slow" "slow" "slow" "slow" "slow" "slow" "slow"
[21] "slow" "slow" "slow" "slow" "slow" "slow" "slow" "slow" "slow" "slow"
[31] "slow" "slow" "slow" "slow" "slow" "slow" "slow" "slow" "slow" "slow"
[41] "slow" "slow" "slow" "fast" "fast" "fast" "fast" "fast" "fast" "fast"
</code></pre>

blocks|key|470065|text|它不是显式存在的，但您可以这样做：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|470066|set.seed(21)
y+<-+1:10
z+<-+rnorm(10)

condition1+<-+TRUE
x1+<-+if(condition1)+y+else+z|code-block|syntax|javascript|470067|或|470068|condition2+<-+sample(c(TRUE,FALSE),10,TRUE)
x2+<-+ifelse(condition2,+y,+z)|470069|两者之间的区别在于condition1必须是长度为1的逻辑向量，而condition2必须是长度与x、y和z相同的逻辑向量。第一个将返回y或z+(整个对象)，第二个将返回y+(condition2==TRUE)或z+(condition2==FALSE)的相应元素。|offset|length|style|CODE|470070|另请注意，如果ifelse、y和z都是长度为1的向量，则condition将比if+/z慢。|470071|entityMap^0|0|0|0|0|9|A|X|A|1D|1|1F|1|1H|1|1W|1|1Y|1|2D|1|2G|G|2Y|1|31|H|0|7|6|E|1|G|1|S|9|13|2|17|1|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|W|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|X|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|Y|8|@$M|Z|N|10|O|P]|$M|11|N|12|O|P]|$M|13|N|14|O|P]|$M|15|N|16|O|P]|$M|17|N|18|O|P]|$M|19|N|1A|O|P]|$M|1B|N|1C|O|P]|$M|1D|N|1E|O|P]|$M|1F|N|1G|O|P]|$M|1H|N|1I|O|P]|$M|1J|N|1K|O|P]]|9|@]|A|$]]|$1|Q|3|R|5|6|7|1L|8|@$M|1M|N|1N|O|P]|$M|1O|N|1P|O|P]|$M|1Q|N|1R|O|P]|$M|1S|N|1T|O|P]|$M|1U|N|1V|O|P]|$M|1W|N|1X|O|P]]|9|@]|A|$]]|$1|S|3|-4|5|6|7|1Y|8|@]|9|@]|A|$]]]|T|$]]

It doesn't explicitly exist, but you can do:

<pre><code>set.seed(21)
y &lt;- 1:10
z &lt;- rnorm(10)

condition1 &lt;- TRUE
x1 &lt;- if(condition1) y else z
</code></pre>

or

<pre><code>condition2 &lt;- sample(c(TRUE,FALSE),10,TRUE)
x2 &lt;- ifelse(condition2, y, z)
</code></pre>

The difference between the two is that <code>condition1</code> must be a logical vector of length 1, while <code>condition2</code> must be a logical vector the same length as <code>x</code>, <code>y</code>, and <code>z</code>. The first will return either <code>y</code> or <code>z</code> (the entire object), while the second will return the corresponding element of <code>y</code> (<code>condition2==TRUE</code>) or <code>z</code> (<code>condition2==FALSE</code>).

Also note that <code>ifelse</code> will be slower than <code>if</code> / <code>else</code> if <code>condition</code>, <code>y</code>, and <code>z</code> are all vectors with length 1.

blocks|key|470111|text|就像其他人所说的那样，使用ifelse，但是您可以定义运算符，以便您几乎拥有三元运算符语法。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|470112|`%25?%25`+<-+function(x,+y)+list(x+=+x,+y+=+y)
`%25:%25`+<-+function(xy,+z)+if(xy$x)+xy$y+else+z

TRUE+%25?%25+rnorm(5)+%25:%25+month.abb
##+[1]++0.05363141+-0.42434567+-0.20000319++1.31049766+-0.31761248
FALSE+%25?%25+rnorm(5)+%25:%25+month.abb
##+[1]+"Jan"+"Feb"+"Mar"+"Apr"+"May"+"Jun"+"Jul"+"Aug"+"Sep"+"Oct"+"Nov"+"Dec"
#+or,+more+generally
condition+%25?%25+value1+%25:%25+value2|code-block|syntax|javascript|470113|如果您定义的运算符没有使用%25符号，那么它实际上是有效的，因此您可以|470114|`?`+<-+function(x,+y)+if(x)+y[[1]]+else+y[[2]]
`:`+<-+function(y,+z)+list(y,+z)

TRUE+?+rnorm(5)+:+month.abb
##+[1]++1.4584104143++0.0007500051+-0.7629123322++0.2433415442++0.0052823403
FALSE+?+rnorm(5)+:+month.abb
##+[1]+"Jan"+"Feb"+"Mar"+"Apr"+"May"+"Jun"+"Jul"+"Aug"+"Sep"+"Oct"+"Nov"+"Dec"|470115|(这之所以有效，是因为:的优先级低于?。)|470116|不幸的是，这会破坏现有的帮助和序列操作符。|470117|entityMap^0|D|6|0|0|D|1|0|0|B|1|I|1|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@$9|V|A|W|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|X|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|Y|8|@$9|Z|A|10|B|C]]|D|@]|E|$]]|$1|M|3|N|5|H|7|11|8|@]|D|@]|E|$I|J]]|$1|O|3|P|5|6|7|12|8|@$9|13|A|14|B|C]|$9|15|A|16|B|C]]|D|@]|E|$]]|$1|Q|3|R|5|6|7|17|8|@]|D|@]|E|$]]|$1|S|3|-4|5|6|7|18|8|@]|D|@]|E|$]]]|T|$]]

Like everyone else said, use <code>ifelse</code>, but you can define operators so that you nearly have the ternary operator syntax.

<pre><code>`%?%` &lt;- function(x, y) list(x = x, y = y)
`%:%` &lt;- function(xy, z) if(xy$x) xy$y else z

TRUE %?% rnorm(5) %:% month.abb
## [1] 0.05363141 -0.42434567 -0.20000319 1.31049766 -0.31761248
FALSE %?% rnorm(5) %:% month.abb
## [1] "Jan" "Feb" "Mar" "Apr" "May" "Jun" "Jul" "Aug" "Sep" "Oct" "Nov" "Dec"
# or, more generally
condition %?% value1 %:% value2
</code></pre>

It actually works if you define the operators without the <code>%</code> signs, so you could have

<pre><code>`?` &lt;- function(x, y) if(x) y[[1]] else y[[2]]
`:` &lt;- function(y, z) list(y, z)

TRUE ? rnorm(5) : month.abb
## [1] 1.4584104143 0.0007500051 -0.7629123322 0.2433415442 0.0052823403
FALSE ? rnorm(5) : month.abb
## [1] "Jan" "Feb" "Mar" "Apr" "May" "Jun" "Jul" "Aug" "Sep" "Oct" "Nov" "Dec"
</code></pre>

(This works because the precedence of <code>:</code> is lower than <code>?</code>.)

Unfortunately, that then breaks the existing help and sequence operators.

blocks|key|686270|text|如果按照以下方式使用，则if的工作方式类似于未矢量化的if：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|686271|`if`(condition,+doIfTrue,+doIfFalse)|code-block|syntax|javascript|686272|与ifelse相比，使用它的优点是当向量化遇到障碍时(也就是说，我得到了标量布尔值和列表/向量值)。|686273|ifelse(TRUE,+c(1,2),+c(3,4))
[1]+1
`if`(TRUE,+c(1,2),+c(3,4))
[1]+1+2|686274|entityMap^0|C|2|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@$9|R|A|S|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|T|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|U|8|@]|D|@]|E|$]]|$1|M|3|N|5|H|7|V|8|@]|D|@]|E|$I|J]]|$1|O|3|-4|5|6|7|W|8|@]|D|@]|E|$]]]|P|$]]

<code>if</code> works like unvectorised ifelse if used in following manner:

<pre><code>`if`(condition, doIfTrue, doIfFalse)
</code></pre>

The advantage of using this over ifelse is when the vectorisation is in the way (i.e I have scalar boolean and list/vector things as a result)

<pre><code>ifelse(TRUE, c(1,2), c(3,4))
[1] 1
`if`(TRUE, c(1,2), c(3,4))
[1] 1 2
</code></pre>

As the question asks, is there a control sequence in R similar to C's <a href="https://stackoverflow.com/a/392946/168775">ternary operator</a>? If so, how do you use it? Thanks!

Does the ternary operator exist in R?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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正如问题所问，在R中是否有类似于C的的控制序列？如果是这样，你如何使用它？谢谢!

问R中是否存在三元运算符？
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问R中是否存在三元运算符？
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