[R] Bug with curve?
Martin Maechler
maechler at stat.math.ethz.ch
Fri Feb 1 15:46:31 CET 2008
>>>>> "BB" == Ben Bolker <bolker at ufl.edu>
>>>>> on Fri, 1 Feb 2008 14:03:15 +0000 (UTC) writes:
BB> Paul Smith <phhs80 <at> gmail.com> writes:
>>
>> Dear All,
>>
>> Take this code:
>>
>> > f <- function(x) exp(-x)*x-0.05
>> > g <- function(x) 0
>> > curve(f,0,5)
>> > curve(g,add=T)
>> Error in xy.coords(x, y) : 'x' and 'y' lengths differ
>> >
>>
>> However, with
>>
>> g <- function(x) x-x
>>
>> no error is generated.
>>
>>
BB> The first paragraph of "details" in the help page
BB> says:
BB> . 'x(t)' or 'expr' (with 'x' inside) must return a numeric of the same
BB> length as the argument 't' or 'x'.
yes, thanks Ben.
BB> So no, technically this is not a bug.
why only "technically"?
Paul wouldn't also be able to integrate(g, .), just
the error message would be slightly more helpful :
Error in integrate(g, 0, 1) :
evaluation of function gave a result of wrong length
BB> The R idiom for adding a horizontal line to the plot is
BB> abline(h=...)
BB> cheers
BB> Ben Bolker
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