Re: [matplotlib-devel] symlog problem

John,

I can't reproduce the error on my intel macbook.
Anyhow, it seems to me a bug in the code and bugs in numpy.
(I'm using numpy version 1.1.1, and I'm not sure these bugs are fixed
in newer numpy. )
Can you try the patch below and see if this fix your problem?

-JJ



Index: lib/matplotlib/scale.py
===================================================================
--- lib/matplotlib/scale.py     (revision 6487)
+++ lib/matplotlib/scale.py     (working copy)
@@ -301,7 +301,8 @@
             self._linadjust = (np.log(linthresh) / self._log_base) / linthre

         def transform(self, a):
-            sign = np.sign(np.asarray(a))
+            a = np.asarray(a)
+            sign = np.sign(a)
             masked = ma.masked_inside(a, -self.linthresh,
self.linthresh, co   False)
             log = sign * ma.log(np.abs(masked)) / self._log_base
             if masked.mask.any():
@@ -328,6 +329,7 @@
             self._linadjust = linthresh / (np.log(linthresh) / self._log_bas

         def transform(self, a):
+            a = np.asarray(a)
             return np.where(a <= self._log_linthresh,
                              np.where(a >= -self._log_linthresh,






On Sat, Dec 6, 2008 at 5:09 PM, John Hunter <jd...@gm...> wrote:
> There appears to be a bug in the 3rd subplot of symlog_demo.py because
> the ticker is generating an OverflowError on my powerbook.
>
> The problem is in SymmetricalLogLocator.__call__ when the vmin, vmax =
> self._transform.transform((vmin, vmax)) call transforms
> vmin,vmax=[-1,1] to [-3.30039237078e+17,1.0] numdec is set to
> 3.30039237078e+17.  Then the while loop runs until I kill the job::
>
>        stride = 1
>        while numdec/stride+1 > self.numticks:
>            stride += 1
>
> This may have something to do with a platform specific floating point
> computations, because I am seeing different results on a linux box I
> am also testing on, but even there the results don't look right.  For
> example, on that box, a 64 bit linux machine, I see [-1,1] transformed
> to [2.18190930577e-316, 6.90437063896e-310] and numdec=-1 but the
> example does run w/o crashing.
>
> In any case, it looks like there is some non-robust computation going
> on, and I'm hoping Michael has a quick insight :-)
>
> JDH
>
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