R help - May 2002 - Re: FW: Contour v Contourplot

Phil,

You write:
>> Using x,y, and z variables in the enclosed test.RData, the command
>> 
>> contour(x,y,z)
>> 
>> produces a lovely 2D plot, whereas
>> 
>> contourplot(z~x*y)
>> 
>> produces the error..
>> 
>> Error in if (lim[1] > lim[2]) stop("Improper value of
limit") :
>>         missing value where logical needed
>> 
>> Any ideas what I'm doing wrong? Many thanks..
Well this took a bit of thought as I am not familiar with lattice. Gave
me the prod I needed to look at it and it was well worth the look.

The lattice functions seem want to have a data.frame rather than a list
of vectors. It doesn't say that in the docs (not that I found but I
didn't look far) so I did:

        load("Test.RData")
        phils.data <- expand.grid(x = x, y = y)
        phils.data$z <- z
        contourplot(z ~ x * y, data = phils.data)

And it worked. The trick is to use expand.grid() to create data.frame
containing one row for each combination x and y and then add z to that.
I think that is what you want.

Use:

        lset(col.whitebg())

Before plots to get rid of the grey background ... better, IMHO)

I think the problem posting to R-Help might be down to your sending an
attachment.

Best wishes,

Mark


--
Mark Myatt


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On Fri, 31 May 2002, Mark Myatt wrote:

[...]
> The lattice functions seem want to have a data.frame rather than a list
> of vectors. It doesn't say that in the docs (not that I found but I
> didn't look far) so I did:
?contourplot does refer you to ?xyplot, and that does stipulate a data
frame.  Perhaps you should look a little further ....

[...]

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272860 (secr)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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