 # [SciPy-user] recursion limit in plot

Neal Becker wrote:

What's wrong here?
This code snippet:

from pylab import plot, show
print Id
print pout

plot (Id, pout)
show()

produces:
['50', '100', '150', '200', '250', '300', '350', '400', '450', '500', '550',
'600', '650', '700', '750', '800', '850', '900', '950', '1000', '1050']
['0', '7.4', '11.4', '14.2', '16.3', '18.1', '19.3', '20.6', '21.6', '22.6',
'23.4', '24.1', '24.9', '25.4', '26.1', '26.5', '26.9', '27.1', '27.3',
'27.4', '27.4']

The problem here is that you're trying to plot lists of strings instead of lists
of numbers. You need to convert all of these values to numbers. However,
matplotlib could behave a bit more nicely in this case rather than simply
recursing until it hits the limit.

Ryan

···

--
Ryan May
School of Meteorology
University of Oklahoma

Ryan May wrote:

Neal Becker wrote:

What's wrong here?
This code snippet:

from pylab import plot, show
print Id
print pout

plot (Id, pout)
show()

produces:
['50', '100', '150', '200', '250', '300', '350', '400', '450', '500', '550',
'600', '650', '700', '750', '800', '850', '900', '950', '1000', '1050']
['0', '7.4', '11.4', '14.2', '16.3', '18.1', '19.3', '20.6', '21.6', '22.6',
'23.4', '24.1', '24.9', '25.4', '26.1', '26.5', '26.9', '27.1', '27.3',
'27.4', '27.4']

The problem here is that you're trying to plot lists of strings instead of lists
of numbers. You need to convert all of these values to numbers. However,
matplotlib could behave a bit more nicely in this case rather than simply
recursing until it hits the limit.

Ok, my debugging tells me the problem comes down to the units support,
specifically this code starting at line 130 in units.py:

if converter is None and iterable(x):
# if this is anything but an object array, we'll assume
# there are no custom units
if isinstance(x, np.ndarray) and x.dtype != np.object:
return None

for thisx in x:
converter = self.get_converter( thisx )
return converter

Because a string is iterable, and even a single character is considered iterable,
this code recurses forever. I can think this can be solved by, in addition to
the iterable() check, make sure that x is not string like. If it is, this will
return None as the converter. Somehow, this actually will then plot properly.
I'm still trying to run down why this works, but I'm running out of time for the
day. I will say that the data set for the line2D object is indeed a masked array
of dtype ('|S4').

Anyone object to adding the check?

In addition, why are we looping over thisx in x but returning inside the loop?
Wouldn't this *always* be the same as x?

Ryan

···

--
Ryan May
School of Meteorology
University of Oklahoma

Ok, my debugging tells me the problem comes down to the units support,
specifically this code starting at line 130 in units.py:

if converter is None and iterable(x):
# if this is anything but an object array, we'll assume
# there are no custom units
if isinstance(x, np.ndarray) and x.dtype != np.object:
return None

for thisx in x:
converter = self.get_converter( thisx )
return converter

Because a string is iterable, and even a single character is considered iterable,
this code recurses forever. I can think this can be solved by, in addition to
the iterable() check, make sure that x is not string like. If it is, this will
return None as the converter. Somehow, this actually will then plot properly.
I'm still trying to run down why this works, but I'm running out of time for the
day. I will say that the data set for the line2D object is indeed a masked array
of dtype ('|S4').

Anyone object to adding the check?

Nope -- good idea

In addition, why are we looping over thisx in x but returning inside the loop?
Wouldn't this *always* be the same as x?

The loop works for generic iterables that are not indexable and also
for length 0 iterables

JDH

···

On Thu, Jan 15, 2009 at 4:58 PM, Ryan May <rmay31@...149...> wrote:

Ryan May wrote:

Ok, my debugging tells me the problem comes down to the units support,
specifically this code starting at line 130 in units.py:

if converter is None and iterable(x):
# if this is anything but an object array, we'll assume
# there are no custom units
if isinstance(x, np.ndarray) and x.dtype != np.object:
return None

for thisx in x:
converter = self.get_converter( thisx )
return converter

Because a string is iterable, and even a single character is considered iterable,
this code recurses forever. I can think this can be solved by, in addition to
the iterable() check, make sure that x is not string like. If it is, this will

Doing this check makes sense.

return None as the converter. Somehow, this actually will then plot properly.
I'm still trying to run down why this works, but I'm running out of time for the
day. I will say that the data set for the line2D object is indeed a masked array
of dtype ('|S4').

Anyone object to adding the check?

In addition, why are we looping over thisx in x but returning inside the loop?
Wouldn't this *always* be the same as x?

The idea is to base the converter selection on the first item instead of checking every item, which would be very slow.

···

Ryan

John Hunter wrote:

Ok, my debugging tells me the problem comes down to the units support,
specifically this code starting at line 130 in units.py:

if converter is None and iterable(x):
# if this is anything but an object array, we'll assume
# there are no custom units
if isinstance(x, np.ndarray) and x.dtype != np.object:
return None

for thisx in x:
converter = self.get_converter( thisx )
return converter

Because a string is iterable, and even a single character is considered iterable,
this code recurses forever. I can think this can be solved by, in addition to
the iterable() check, make sure that x is not string like. If it is, this will
return None as the converter. Somehow, this actually will then plot properly.
I'm still trying to run down why this works, but I'm running out of time for the
day. I will say that the data set for the line2D object is indeed a masked array
of dtype ('|S4').

Anyone object to adding the check?

Nope -- good idea

Ok, I'll check it in when I have a chance to run backend_driver.py and makes sure
nothing breaks. (Not that it should). I'll also take a crack at adding a test.

For future reference, plotting lists/arrays of strings works (at least for lines)
because Path calls .astype() on the arrays passed in, which will do the
conversion for us. So (part of) matplotlib actually does support plotting
sequences of string representations of numbers, it was just hindered by the unit
check.

In addition, why are we looping over thisx in x but returning inside the loop?
Wouldn't this *always* be the same as x?

The loop works for generic iterables that are not indexable and also
for length 0 iterables

Ok, that makes sense.

Ryan

···

On Thu, Jan 15, 2009 at 4:58 PM, Ryan May <rmay31@...149...> wrote:

--
Ryan May