Revision of errors from Wed, 09/02/2009 - 07:07

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General strategies for locating errors

  • Use the traceback() function in R after an error occurs.
    It will print out the sequence of function calls that lead to the error.

"Argument is missing, with no default"

  • Variations include:
    • Error in single.na(to) : argument is missing, with no default
  • Typical cause: A leading or trailing comma in your code makes R think that you wanted to pass in a parameter, but left it empty (hence "missing, with not default")
    • Examples:
    • leading comma
      to=c(,'x','y','z')
    • trailing comma
      mxMatrix("Name"
      	nrow=3,ncol=3,free=TRUE, values=.5,
      )
    • Cure: remove the errant comma

Error in convertVFN(... NAs introduced by coercion

  • Whenever you see NAs being introduced by coercion, suspect that you have the wrong type of value for a parameter: For instance, perhaps you are setting a number to string or vice versa... the coercion will fail, leaving an NA, which R warns you about.
  • Example:
    #You say:
    	mxMatrix(type = "Full", nrow = 1, ncol = 1, free = FALSE, 
    	       values = "l1", labels = "aa", 
    	       lbound = 0, ubound = 2, name = "la"),
     

    We try and convert the character "l1" to a numeric value, can't, return an NA... hence the error: NAs induced by coercion.

  • The error:
    	Warning messages:
    	1: In convertVFN(values, free, labels, lbound, ubound, nrow, ncol) :
    	  NAs introduced by coercion...
  • Solution: in this case, set the value to a numeric, (and remember that to equate values, you set the labels to be the same)