I've been thinking of adding the possibility of including "z" among the
axes to be logged in image, contour, and persp. In the first two, it
would only affect where the breaks were set if they are calculated
automatically; it would have a bigger effect in persp.
For example,
image(x, y, z, log="z")
would set 12 colours evenly spaced on a log scale of the z values. (12
because that's the default).
We already support
image(x, y, z, log="x")
to scale the x axis (though there's a spurious warning; I'll fix that).
image(z, log="x")
fails because it tries to take a log of zero.
Does it seem like a good idea for these 3D functions to support log="z"
the way 2D functions do?
Duncan Murdoch
R-devel (AT) r-project (DOT) org mailing list

"Duncan" == Duncan Murdoch <murdoch (AT) stats (DOT) uwo.ca>
on Tue, 09 May 2006 18:41:09 -0400 writes:

DuncanI've been thinking of adding the possibility of
Duncanincluding "z" among the axes to be logged in image,
Duncancontour, and persp. In the first two, it would only
Duncanaffect where the breaks were set if they are
Duncancalculated automatically; it would have a bigger
Duncaneffect in persp.

DuncanFor example,

Duncanimage(x, y, z, log="z")

Duncanwould set 12 colours evenly spaced on a log scale of
Duncanthe z values. (12 because that's the default).

DuncanWe already support

Duncanimage(x, y, z, log="x")

Duncanto scale the x axis (though there's a spurious
Duncanwarning; I'll fix that).

Duncanimage(z, log="x")

Duncanfails because it tries to take a log of zero.

DuncanDoes it seem like a good idea for these 3D functions
Duncanto support log="z" the way 2D functions do?

Yes, I think it's a good idea.

You forgot to mention filled.contour()
which is image() + "color - legend"
For that one, it would be particularly useful to automatically
get a "evenly space in log-scale" one.

DuncanDuncan Murdoch

Note that for things like the above, I have added
a simple function lseq() in package 'sfsmisc' -- which I have
contemplated moving to R. Maybe this could happen at the same
time and you could make use of it for the above.

Martin

R-devel (AT) r-project (DOT) org mailing list

5/10/2006 4:23 AM, Martin Maechler wrote:
"Duncan" == Duncan Murdoch <murdoch (AT) stats (DOT) uwo.ca>
on Tue, 09 May 2006 18:41:09 -0400 writes:

DuncanI've been thinking of adding the possibility of
Duncanincluding "z" among the axes to be logged in image,
Duncancontour, and persp. In the first two, it would only
Duncanaffect where the breaks were set if they are
Duncancalculated automatically; it would have a bigger
Duncaneffect in persp.

DuncanFor example,

Duncanimage(x, y, z, log="z")

Duncanwould set 12 colours evenly spaced on a log scale of
Duncanthe z values. (12 because that's the default).

DuncanWe already support

Duncanimage(x, y, z, log="x")

Duncanto scale the x axis (though there's a spurious
Duncanwarning; I'll fix that).

Duncanimage(z, log="x")

Duncanfails because it tries to take a log of zero.

DuncanDoes it seem like a good idea for these 3D functions
Duncanto support log="z" the way 2D functions do?

Yes, I think it's a good idea.

You forgot to mention filled.contour()
which is image() + "color - legend"
For that one, it would be particularly useful to automatically
get a "evenly space in log-scale" one.

Thanks for pointing that out. This is a little tricky: I think
filled.contour would want evenly spaced contours, but use the axTicks()
version of pretty labels on the legend; but contour() would probably
want the contours themselves to be at nice round values.

It looks as though I'll need to think about adding a log=TRUE option to
pretty(), to expose or duplicate the internal code that sets log axes.
(axTicks is close, but I don't think it allows for automatic computation
of axp[3]).

Duncan

DuncanDuncan Murdoch

Note that for things like the above, I have added
a simple function lseq() in package 'sfsmisc' -- which I have
contemplated moving to R. Maybe this could happen at the same
time and you could make use of it for the above.

Martin

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