blocks|key|715801|text|assertive和assertthat包具有更具可读性的检查函数。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|715802|library(assertthat)
assert_that(length(unique(nchar(check)))+==+1)
##+Error:+length(unique(nchar(check)))+==+1+are+not+all+true.

library(assertive)
assert_is_scalar(unique(nchar(check)))
##+Error:+unique(nchar(check))+does+not+have+length+one.

if(!is_scalar(unique(nchar(check))))+
{
++stop("Elements+of+check+have+different+numbers+of+characters.")
}
##+Error:+Elements+of+check+have+different+numbers+of+characters.|code-block|syntax|javascript|715803|entityMap^0|0|9|A|A|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]|$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|R|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|S|8|@]|D|@]|E|$]]]|L|$]]

The <code>assertive</code> and <code>assertthat</code> packages have more readable check functions.

<pre><code>library(assertthat)
assert_that(length(unique(nchar(check))) == 1)
## Error: length(unique(nchar(check))) == 1 are not all true.

library(assertive)
assert_is_scalar(unique(nchar(check)))
## Error: unique(nchar(check)) does not have length one.

if(!is_scalar(unique(nchar(check)))) 
{
 stop("Elements of check have different numbers of characters.")
}
## Error: Elements of check have different numbers of characters.
</code></pre>

blocks|key|716000|text|可以将自定义消息作为标签添加到表达式中：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|716001|stopifnot("Elements+of+your+input+vector+do+not+have+the+same+length!"+=
++length(unique(nchar(check)))+==+1)

#+Error:+Elements+of+your+input+vector+do+not+have+the+same+length!|code-block|syntax|javascript|716002|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

A custom message can be added as a label to your expression:
<pre><code>stopifnot(&quot;Elements of your input vector do not have the same length!&quot; =
 length(unique(nchar(check))) == 1)

# Error: Elements of your input vector do not have the same length!
</code></pre>

blocks|key|715944|text|将stopifnot嵌入到tryCatch中，然后使用自定义消息使用stop重新转换异常，会怎么样呢？|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|715945|类似于：|715946|tryCatch(stopifnot(...,error=stop("Your+customized+error+message"))|code-block|syntax|javascript|715947|与其他一些解决方案不同，这不需要额外的包。与结合使用if语句和stop相比，当您使用新的R版本时，可以保留stopifnot的性能优势。从R版本3.5.0开始，stopifnot会按顺序计算表达式，并在第一次失败时停止。|715948|entityMap^0|1|9|D|8|Y|4|0|0|0|Q|2|V|4|1H|9|28|9|0^^$0|@$1|2|3|4|5|6|7|Q|8|@$9|R|A|S|B|C]|$9|T|A|U|B|C]|$9|V|A|W|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|X|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|Y|8|@]|D|@]|E|$K|L]]|$1|M|3|N|5|6|7|Z|8|@$9|10|A|11|B|C]|$9|12|A|13|B|C]|$9|14|A|15|B|C]|$9|16|A|17|B|C]]|D|@]|E|$]]|$1|O|3|-4|5|6|7|18|8|@]|D|@]|E|$]]]|P|$]]

What about embedding the <code>stopifnot</code> into <code>tryCatch</code> and then recasting the exception with <code>stop</code> using customized message?

Something like:

<pre><code>tryCatch(stopifnot(...,error=stop("Your customized error message"))
</code></pre>

Unlike some other solutions this does not require additional packages. Compared to using <code>if</code> statement combined with <code>stop</code> you retain the performance advantages of <code>stopifnot</code>, when you use new R versions. Since R version 3.5.0 <code>stopifnot</code> evaluates expressions sequentially and stops on first failure.

blocks|key|715664|text|或者你可以把它打包起来。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|715665|assert+<-+function+(expr,+error)+{
++if+(!+expr)+stop(error,+call.+=+FALSE)
}|code-block|syntax|javascript|715666|因此，您需要：|715667|>+check+=+c("x",+"xx",+"xxx")
>+assert(length(unique(nchar(check)))+==+1,+"Elements+of+your+input+vector+do+not+have+the+same+length!")

Error:+Elements+of+your+input+vector+do+not+have+the+same+length!|715668|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

Or you could package it up.

<pre><code>assert &lt;- function (expr, error) {
 if (! expr) stop(error, call. = FALSE)
}
</code></pre>

So you have:

<pre><code>&gt; check = c("x", "xx", "xxx")
&gt; assert(length(unique(nchar(check))) == 1, "Elements of your input vector do not have the same length!")

Error: Elements of your input vector do not have the same length!
</code></pre>

blocks|key|500198|text|我建议您查看Hadley的testthat包。它允许进行直观的测试:函数的名称很棒，编写它们的方式就像一句话--“我期望length(unique(nchar(check)))恰好%7C大约为1”。产生的错误是信息性的。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|500199|查看此处：http://journal.r-project.org/archive/2011-1/RJournal_2011-1_Wickham.pdf|500200|在你的情况下，|500201|>+library(testthat)
>+check+=+c("x",+"xx",+"xxx")
>+expect_that(length(unique(nchar(check))),+equals(1))
Error:+length(unique(nchar(check)))+not+equal+to+1
Mean+relative+difference:+2|code-block|syntax|javascript|500202|还要注意的是，你不会有@Andrie提到的问题，有时不得不考虑使用stopifnot的双重否定。我知道这看起来很简单，但它让我很头疼！|500203|entityMap|0|LINK|mutability|MUTABLE|url|http://journal.r-project.org/archive/2011-1/RJournal_2011-1_Wickham.pdf^0|D|8|1O|S|0|5|1Z|0|0|0|0|X|9|0^^$0|@$1|2|3|4|5|6|7|Y|8|@$9|Z|A|10|B|C]|$9|11|A|12|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|13|8|@]|D|@$9|14|A|15|1|16]]|E|$]]|$1|H|3|I|5|6|7|17|8|@]|D|@]|E|$]]|$1|J|3|K|5|L|7|18|8|@]|D|@]|E|$M|N]]|$1|O|3|P|5|6|7|19|8|@$9|1A|A|1B|B|C]]|D|@]|E|$]]|$1|Q|3|-4|5|6|7|1C|8|@]|D|@]|E|$]]]|R|$S|$5|T|U|V|E|$W|X]]]]

I would recommend you check out Hadley's <code>testthat</code> package. It allows for intuitive testing: the names of the functions are great and the way you write them is like a sentence -- "I expect that <code>length(unique(nchar(check)))</code> is [exactly|approximately] 1". The errors produced are informative.

See here:
<a href="http://journal.r-project.org/archive/2011-1/RJournal_2011-1_Wickham.pdf" rel="nofollow">http://journal.r-project.org/archive/2011-1/RJournal_2011-1_Wickham.pdf</a>

In your case,

<pre><code>&gt; library(testthat)
&gt; check = c("x", "xx", "xxx")
&gt; expect_that(length(unique(nchar(check))), equals(1))
Error: length(unique(nchar(check))) not equal to 1
Mean relative difference: 2
</code></pre>

Also note that you don't have the problem that @Andrie referenced with sometimes having to think about double negatives with <code>stopifnot</code>. I know it seems simple, but it caused me many headaches!

blocks|key|715886|text|已经提供的答案非常好，而我的答案只是对这个集合的补充。对于某些人来说，以以下函数的形式使用一行程序可能会更方便：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|715887|stopifnotinform+<-+function(...,+message+=+"err")+{
++args+<-+list(...)
++if+(length(args)+==+0)+{
++++return(NULL)
++}
++for+(i+in+1:length(args))+{
++++result+<-+args[[i]]
++++if+(is.atomic(result)+&&+result+==+FALSE)+{
++++++stop(message)
++++}
++}
}

#+throws+an+error
stopifnotinform(is.integer(1L),+is.integer(2),+message+=+"Some+number(s)+provided+is+not+an+integer")
#+continues+with+execution
stopifnotinform(is.integer(1L),+is.integer(2L),+message+=+"Some+number(s)+provided+is+not+an+integer")|code-block|syntax|javascript|715888|请记住，对于...中的所有参数，此解决方案只为您提供一条(公共)错误消息。|offset|length|style|CODE|715889|entityMap^0|0|0|6|3|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@$I|R|J|S|K|L]]|9|@]|A|$]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

The answers already provided are quite good, and mine is just an addition to that collection. For some people it could be more convenient to use one-liner in form of the following function:

<pre><code>stopifnotinform &lt;- function(..., message = "err") {
 args &lt;- list(...)
 if (length(args) == 0) {
 return(NULL)
 }
 for (i in 1:length(args)) {
 result &lt;- args[[i]]
 if (is.atomic(result) &amp;&amp; result == FALSE) {
 stop(message)
 }
 }
}

# throws an error
stopifnotinform(is.integer(1L), is.integer(2), message = "Some number(s) provided is not an integer")
# continues with execution
stopifnotinform(is.integer(1L), is.integer(2L), message = "Some number(s) provided is not an integer")
</code></pre>

Bear in mind that this solution provides you with only one (common) error message for all parameters in <code>...</code>.

blocks|key|500480|text|试试这个：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|500481|same_length+<-+FALSE
stopifnot("Elements+of+your+input+vector+do+not+have+the+same+length!"+=+same_length)
#>+Error+:+Elements+of+your+input+vector+do+not+have+the+same+length!|code-block|syntax|javascript|500482|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Try this:
<pre class="lang-r prettyprint-override"><code>same_length &lt;- FALSE
stopifnot(&quot;Elements of your input vector do not have the same length!&quot; = same_length)
#&gt; Error : Elements of your input vector do not have the same length!
</code></pre>

I am using <code>stopifnot</code> and I understand it just returns the first value that was not <code>TRUE</code>. I f that is some freaky dynamic expression someone who is not into the custom function cannot really make something out of that. So I would love to add a custom error message. Any suggestions?

<pre><code>Error: length(unique(nchar(check))) == 1 is not TRUE
</code></pre>

Basically states that the elements of the vector <code>check</code> do not have the same length.
Is there a way of saying: <code>Error: Elements of your input vector do not have the same length!</code>?

Better error message for stopifnot?

我使用的是stopifnot，我知道它只返回第一个非TRUE的值。如果这是一些奇怪的动态表达式，那么对自定义函数不熟悉的人就不能真正理解它。所以我很乐意添加一个自定义的错误消息。有什么建议吗？Error: length(unique(nchar(check))) == 1 is not TRUE基本上说明向量check的元素不具有相同的长度。有没有一种方式可以说：Error: Elements o

问对stopifnot更好的错误信息？
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问对stopifnot更好的错误信息？
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