# [Numpy-discussion] NumPy Histogram for Tentative NumPy Tutorial Questions

josef.pktd@gmai... josef.pktd@gmai...
Thu Nov 26 20:49:38 CST 2009

```On Thu, Nov 26, 2009 at 9:48 PM,  <josef.pktd@gmail.com> wrote:
> On Thu, Nov 26, 2009 at 8:18 PM, Wayne Watson
> <sierra_mtnview@sbcglobal.net> wrote:
>> Yes, I'm just beginning to deal with the contents of NumPy, SciLab, and
>> SciPy. They all have seemed part of one another, but I think I see how
>> they've divided up the game. NumPy has no graphics. PyLab has them,
>> basically under matplotlib. histogram seems a bit odd to me.  Here's
>> what I mean. I chopped some lines out of the other program:
>> import numpy
>> import pylab
>> #v = [5,5,2,2,2,6,4,4,3,3]
>> v=[1,2,3,4]
>> # Plot a normalized histogram
>> pylab.hist(v, bins=8, normed=1)
>> pylab.show()
>>
>> If it's run, I would have expected 4 bars separated by the same
>> distance. The commented version of v is worse. It gives bar heights that
>> are of an even height. Using more bins gives some odd length bars. Maybe
>> an x row would help.
>>
>> While I'm at it what's with the two arrows at the bottom and the cross?
>> I see the cross moves the drawing area, but does anyone really want to
>> do that? The arrows seem to only move the drawing area slightly. Zoom,
>> pencil,  seems pretty offbeat.
>
> Do you mean this http://matplotlib.sourceforge.net/users/navigation_toolbar.html
>
> Zoom is convenient when you have for example a thousand points with
> lots of variation in one graph.
> Browsing some examples in the matplotlib docs might be useful to get a
> basic idea of it
> e.g http://matplotlib.sourceforge.net/gallery.html
>
> The main docs for numpy scipy start here http://docs.scipy.org/doc/

http://docs.scipy.org/doc/

I guess a linebreak got wrongly interpreted

Josef

> many/most of the numpy functions have by now examples in the reference
> guide and docstrings and might be more up to date than the tutorial.
> It might be helpful to browse them in parallel to the tutorial.
>
> Josef
>
>>
>> Pauli Virtanen wrote:
>>> to, 2009-11-26 kello 15:08 -0800, Wayne Watson kirjoitti:
>>>
>>>> I guess the answer is easy about why a plot is not produced. The remark
>>>> in the histogram line says this will not work in numpy. Oh, well.
>>>>
>>>
>>> It works as it is intended to work. Numpy's histogram function just
>>> computes the histogram -- you have to plot it yourself.
>>>
>>> Indeed, the next two lines in the example use Matplotlib (ie. pylab) to
>>> plot the histogram.
>>>
>>>
>>
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>
```