Yes, this one is a bug in CreateAtVector, plot.c.
It already has the lines:
/* Debugging: When does the following happen... ? */
if (umin > umax)
warning("CreateAtVector \"log\"(from axis()): "
"usr[0] = %g > %g = usr[1] !", umin, umax);
And now we know that it happens if (and only if?????) the logarithmic
scale is not very small (i.e. axp[2] > 0, this is equal to R's
par("yaxp")[3] in your example) and the axis are reversed (umin > umax).
I'll try to provide a fix which should be possible by reversing
arguments axp and usr in this case and returning a reversed at ...
Uwe Ligges
marquardt.christian@gmail.com wrote:
Full_Name: Christian Marquardt
Version: 2.1.0
OS: Linux (Redhat 9)
Submission from: (NULL) (151.170.240.10)
Following the advice of a reader of R-help, I would now like to submit this as a
bug report:
Say we have
x = seq(1,3, by = 0.01)
y = exp(x)
Plotting and reversing linear axis is fine
plot(x,y)
plot(x,y, ylim = c(30,1))
as is a usual log-plot:
plot(x,y, log = "y", ylim = c(1,30))
However,
plot(x,y, log = "y", ylim = c(30,1))
fails with
Error in axis(2, ...) : log - axis(), 'at' creation, _SMALL_ range:
invalid {xy}axp or par;
axp[0]= 10, usr[0:1]=(34.3721,0.872801)
In addition: Warning message:
CreateAtVector "log"(from axis()): usr[0] = 34.3721 > 0.872801 = usr[1] !
According to Petr Pikal <petr.pikal -at- precheza.cz>, replacing the ylim
argument by ylim = c(30,1.2) helps in the above example; but in my real world
applications, it's actually difficult to find a working value for ylim.
I hope this is useful,
Christian.
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