Xiaotao Luo - 5 months ago 48

R Question

In R, I wrote a function like:

`fun <- function(A, B, C, D) {}`

So, after writing a function, I must do argument checking first:

`arguments = {A, B, C, D, ...}`

But about these arguments, some is required, some is not, and the

So I must do things in the beginning of

- Is some required arguments missing
- Is all arguments following the rules:
**class(data type)**or**A must be in range [1:3]**

To accomplish this, I did things likeļ¼

`if(A Follow_the_rule){}`

if(B Follow_the_rule){}

if(C Follow_the_rule){}

...

The code above, so much

So the question is:

Any help will be appreciated.

Answer

Have a look at `?stopifnot`

which does exactly what you want. It checks for the condition within and stops if the condition is not given. The same as in `if`

, you can concatenate conditions with `&&`

or `||`

and `&`

amd `|`

. See information with e.g. `?"&"`

. Further helpful may also be `all`

or `any`

to check if all elements of a given vector fulfill the condition or any, respectively. Some examples:

```
foo <- function(A, B, C){
stopifnot(!missing(C), !missing(B), !missing(A)) ##A, B, C not missing, then continue
stopifnot(class(B)=="matrix") ## B is a matrix, then continue
stopifnot(class(B)==class(C), all(B > C)) ## class B is class C and all elements of B are greater than C
stopifnot((length(A)>1 && !any(is.na(A))) || all(A==0)) ## (A has more than 1 element and no element is NA) or all elements of A are 0.
stopifnot(all(A > 2), all(A < 10)) ## all elements of A are between 2 and 10, else stop.
#... further code
}
```

The conditions above may not fit together in this combination, but I think there are enough examples for you to adapt to your problem. Of course you could write all in one `stopifnot`

, but it is more useful to group the conditions if there are many, because the condition which stops the function is printed as error code. So the more `stopifnot`

you have, the more precise is the error information you get.