[R] Suppressing error messages printed in xyplot() with panel function

[Adam Zeilinger]

Dear Deepayan and Dennis,

Both of your proposed fixes worked perfectly.  Thank you!

Adam


On 8/24/2011 9:47 PM, Deepayan Sarkar wrote:
> On Thu, Aug 25, 2011 at 1:00 AM, Adam Zeilinger<zeil0006 at umn.edu>  wrote:
>> Hello,
>>
>> I am using the xyplot() function to create a series of scatterplot panels
>> with lines of best fit.  To draw the lines of best fit for each panel, I am
>> using a panel function.  Here's an example:
>>
>>> species<- as.character(c(rep(list("A", "B", "A"), 10), "B"))
>>> year<- as.character(c(rep(list("2009", "2009", "2010"), 10), "2010"))
>>> x<- rnorm(31, mean = 50, sd = 1)
>>> y<- 3*x + 20
>>> ex.data<- data.frame(cbind(species, year, x, y))
>>> ex.data$x<- as.numeric(ex.data$x)
>>> ex.data$y<- as.numeric(ex.data$y)
>>> xyplot(y ~ x|species*year, data = ex.data,
>> +   panel = function(x, y) {
>> +   panel.xyplot(x, y, pch=16, col="black")
>> +   panel.abline(lm(y ~ x))})
>>
>> With my data set, there are some panels with less than 2 data points.  In
>> these panels, an error message is printed in the panel, something like:
>> "Error using packet 4 missing value where TRUE/FALSE needed."
>>
>> In the panels with error messages, I want to keep the panels but suppress
>> the error message, such that the panel is blank or has only one datum.  How
>> do I do suppress the printing of the error message?
> Generally speaking, suppressing error messages should not be your
> first instinct. If you know why the error is happening, it's better to
> make sure it never happens, e.g., with something like
>
>     if (length(x)>= 2) panel.abline(lm(y ~ x))
>
> Of course, as Dennis says, in this case you can take advantage of the
> 'type' argument, which already implements what you want.
>
> -Deepayan


-- 

Adam Zeilinger
Ph. D Candidate
Conservation Biology Program
University of Minnesota
Saint Paul, MN
www.linkedin.com/in/adamzeilinger