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

Wayne Watson sierra_mtnview@sbcglobal....
Thu Nov 26 19:18:39 CST 2009


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.

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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