Unused arguments in R

Question

In R  is it possible to have a the software ignore the fact that there are unused arguments defined when a module is run   For example  I have a module multiply a b   which returns the product of a and b   I will receive an error if I call the module like so   multiply a 20 b 30 c 10    Returning an error on this just seems a bit unnecessary  since the required inputs a and b have been specified   Is it possible to avoid this bad behaviour   An easy solution would be just to stop specifying c  but that doesn t answer why R behaves like this   Is there another way to solve this

User · Accepted Answer

Change the definition of multiply to take additional unknown arguments   multiply  lt - function a  b             Original code

User · Answer

I had the same problem as you  I had a long list of arguments  most of which were irrelevant  I didn t want to hard code them in   This is what I came up with  library magrittr  do func ignore things  lt - function data  what       acceptable args  lt - data names data   in   formals what    gt   names       do call what  acceptable args   gt   as list     do func ignore things c n   3  hello   12  mean   -10    rnorm     -9 230675 -10 503509 -10 927077

User · Answer

The R utils package has a function called doCall which is like do call  but it does not return an error if unused arguments are passed   multiply  lt - function a  b  a   b    these will fail multiply a   20  b   30  c   10    Error in multiply a   20  b   30  c   10    unused argument  c   10  do call multiply  list a   20  b   30  c   10     Error in  function  a  b     unused argument  c   10     R utils  doCall will work R utils  doCall multiply  args   list a   20  b   30  c   10      1  600   it also does not require the arguments to be passed as a list R utils  doCall multiply  a   20  b   30  c   10     1  600

User · Answer

One approach  which I can t imagine is good programming practice  is to add the     which is traditionally used to pass arguments specified in one function to another    gt  multiply  lt - function a b  a b  gt  multiply a   2 b   4 c   8  Error in multiply a   2  b   4  c   8    unused argument s   c   8   gt  multiply2  lt - function a b      a b  gt  multiply2 a   2 b   4 c   8   1  8   You can read more about     is intended to be used here

User · Answer

You could use dots      in your function definition   myfun  lt - function a  b          cat a b     myfun a 4 b 7 hello 3     4 7

[r] Unused arguments in R

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