R-<需要TRUE/FALSE的缺失值“ [英] R - " missing value where TRUE/FALSE needed "

查看：111 发布时间：2020/11/26 5:31:25 r if-statement syntax

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我正在尝试在R中执行以下代码

I'm trying to execute the following code in R

comments = c("no","yes",NA)
for (l in 1:length(comments)) {
    if (comments[l] != NA) print(comments[l]);
}

但是我遇到了错误

Error in if (comments[l] != NA) print(comments[l]) : missing value where TRUE/FALSE needed

这是怎么回事?

检查命令:NA!=NA:您将得到结果NA，因此出现错误消息.

check the command : NA!=NA : you'll get the result NA, hence the error message.

您必须使用函数is.na来使if语句正常工作(通常，最好使用此函数来检查NA值):

You have to use the function is.na for your ifstatement to work (in general, it is always better to use this function to check for NA values) :

comments = c("no","yes",NA)
for (l in 1:length(comments)) {
    if (!is.na(comments[l])) print(comments[l])
}
[1] "no"
[1] "yes"

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R-&lt;需要TRUE/FALSE的缺失值“ [英] R - &quot; missing value where TRUE/FALSE needed &quot;