捕获库函数的输出

Question

我真的很茫然.我在堆栈上发现了一些关于如何重定向函数输出的线程,但是在我的情况下它似乎都没有.

我正在使用来自library(forecast)许多(生成的)时间序列的arima ,其中一些具有不良属性,这导致auto.arima()打印出错误和警告.无论如何我都无法捕捉到这个错误,无论是通过tryCatch还是capture.output()(只捕获正常的预测).

目标是捕获下面示例抛出的错误消息(和警告)并对其作出反应.所以基本上最后我会以某种变量的形式出现错误和预测(尽管是错误的).

我感谢任何建议,以下是产生错误的最小示例:

library(forecast)
testt <- c(826,816,839,995,697)
testend <- c(2015,164)
testseries <- ts(testt,end=testend,frequency=365)
auto.arima(testseries)
#tryCatch not working:
testfc <- tryCatch(forecast(auto.arima(testseries),h=1), error=function(e) NA)
#capture.output not working:
result <- capture.output(auto.arima(testseries))

Answer 1

您可以使用type="message"参数来捕获错误和警告capture.output.type可以是"输出",它捕获功能输出,或"消息",它捕获错误和警告.下面的函数sapply用于允许您capture.output使用每个参数运行一次,将结果存储在列表中.

capture.errors = function(type, data) {
  sapply(type, function(type) {
    capture.output(auto.arima(data), type=type)
  }, simplify=FALSE)
}

out = capture.errors(c("output","message"), testseries)

out

$output
[1] "Series: data "                                    
[2] "ARIMA(0,0,0) with non-zero mean "                 
[3] ""                                                 
[4] "Coefficients:"                                    
[5] "      intercept"                                  
[6] "       834.6000"                                  
[7] "s.e.    42.4746"                                  
[8] ""                                                 
[9] "sigma^2 estimated as 9020:  log likelihood=-29.86"
[10] "AIC=63.73   AICc=69.73   BIC=62.94"               

$message
[1] "Error in arima(x, order = c(1, d, 0), xreg = xreg) : "
[2] "  non-stationary AR part from CSS"                    
[3] "In addition: Warning message:"                        
[4] "In auto.arima(data) : Unable to calculate AIC offset" 

由于捕获模型输出capture.output可能不如捕获模型对象中的"实际"输出那样有用,因此下面的函数可能会更好.它返回一个包含模型对象的列表以及任何错误或警告消息:

capture = function(data) {
list(model=auto.arima(data),
     message=capture.output(auto.arima(data), type="message"))
}

模型对象以通常的方式提供,所以下面我只看一下消息输出.

out1 = capture(testseries)

# Show any errors and warnings
out1[["message"]]
[1] "Error in arima(x, order = c(1, d, 0), xreg = xreg) : "
[2] "  non-stationary AR part from CSS"                    
[3] "In addition: Warning message:"                        
[4] "In auto.arima(data) : Unable to calculate AIC offset" 

out2 = capture(cumsum(rnorm(100)))

# No errors or warnings with this data set
out2[["message"]]
character(0)