# [R] Help with error in "if then" statement

John Kane jrkrideau at yahoo.ca
Sat Jul 12 17:12:45 CEST 2008

```As the note at the bottom says provide commented, minimal, self-contained, reproducible code.

It is difficult to comment on a loop when we have no code to read.

--- On Fri, 7/11/08, Andrew Rominger <rominger at stanford.edu> wrote:

> From: Andrew Rominger <rominger at stanford.edu>
> Subject: [R] Help with error in "if then" statement
> To: r-help at r-project.org
> Received: Friday, July 11, 2008, 12:48 PM
> Dear list,
>
> I'm afraid this is a mundane question.  Here's the
> background: I've
> produced a function which allows me to sequentially measure
> angles and
> distances from a specified reference point to a curve
> defined by
> empirical data points while (i.e. using a while loop) the
> angle being
> measured is within certain bounds.  Because the curve is
> circular I
> need to pars the data into basically an "upper"
> curve and "lower"
> curve.  I tried to do this with an if statement,
> specifically:
>
> ycrit<-subset(data,subset=data\$x==min(data\$x)
> y.max<-length*sin(angle)+y.ref #length, angle and y.ref
> are given
> if(y.max<ycrit){
> ........
> }
>
> Now the problem:  The while loop works for 4 iterations,
> until I get
> the error message:
>
> "Error in if (y.max < ycrit) { : missing value
> where TRUE/FALSE needed"
>
> When I forced the function to print y.max and ycrit for
> each iteration
> of the while loop, it returns finite real numbers,
> including ycrit =
> 153.5 and y.max = 245.16 for the step which returns the
> error message.
>
> Any ideas about what's going on here--why does R
> "think" that
> 245.16<153.5 is "missing," or is anything
> other than TRUE/FALSE?  Am I
> using "if" incorrectly?  In which case would it
> be more appropriate to
> perhaps create subsets of the data points based on < or
> > ycrit?
>
> Thanks in advance for any guidance--
> Andy
>
> --
> Andrew J. Rominger
> Department of Biological Sciences
> Stanford University
> rominger at stanford.edu
>
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