if/while (condition) {: 缺少 TRUE/FALSE 需要的值

问题描述

我收到此错误消息:

Error in if (condition) { : missing value where TRUE/FALSE needed

或

Error in while (condition) { : missing value where TRUE/FALSE needed

这是什么意思，我该如何预防?

What does it mean, and how do I prevent it?

推荐答案

condition 的评估结果为 NA.if 条件必须具有 TRUE 或 FALSE 结果.

The evaluation of condition resulted in an NA. The if conditional must have either a TRUE or FALSE result.

if (NA) {}
## Error in if (NA) { : missing value where TRUE/FALSE needed

由于计算结果，这可能会意外发生:

This can happen accidentally as the results of calculations:

if(TRUE && sqrt(-1)) {}
## Error in if (TRUE && sqrt(-1)) { : missing value where TRUE/FALSE needed

要测试对象是否丢失，请使用 is.na(x) 而不是 x == NA.

另见相关错误:

if/while(条件)错误{:参数长度为零

if/while(条件)错误:参数不可解释为逻辑

if (NULL) {}
## Error in if (NULL) { : argument is of length zero

if ("not logical") {}
## Error: argument is not interpretable as logical

if (c(TRUE, FALSE)) {}
## Warning message:
## the condition has length > 1 and only the first element will be used

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