Equivalent of "throw" in R
How does one "throw" an erro开发者_如何转开发r in R? I have a function that takes a data frame and some column names and does stuff with them. If the columns don't exist, I want the function to stop and to stop all functions depending on it.
I have looked at recover
and browse
and traceback
but, well, they seemed to be close but not what I am looking for.
See help(tryCatch)
:
Conditions are signaled by '
signalCondition
'. In addition, the
'stop
' and 'warning
' functions have been modified to also accept
condition arguments.
and later under 'See Also':
'
stop
' and 'warning
' signal conditions, and 'try
' is essentially a simplified version of 'tryCatch
'.
so you probably want stop
.
Simple example:
f <- function(a, b){
if (a == 0){
stop("error message")
}
}
Beyond the base functions that Dirk mentions:
The R.oo package has additional exception handling functionality, including a throw() function which is very useful. You can catch exceptions with the usual try or trycatch functions:
> try(throw("Division by zero.")); print("It's ok!");
Error: [2009-10-22 10:24:07] Exception: Division by zero.
[1] "It's ok!"
You can read more about it here: http://www1.maths.lth.se/help/R/R.oo/
Actually the function stopifnot
is very convenient to implement sanity checks in your code. It takes in several logical expressions and returns an error if any of them evaluates to false.
Example: To check if column 'c' exists in the dataframe 'df':
df <- data.frame(a = numeric(), b = numeric())
stopifnot(!is.null(df$c))
This will throw the following error:
Error: !is.null(df$c) is not TRUE
You can check if the column exists and do whatever your want.
Suppose a data.frame
named df1
and checking if column col1
exists:
if(! any(grepl('^col1$',colnames(df1)))) stop("nonexistent column")
or
if(! any(grepl('^col1$',colnames(df1)))) return(-1)
For instance
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