In [25]:

    

def plotband(x, y, ups, downs, color='#0067ea', alpha=.25, **kwargs):
    """
    plots a line surrounded by a ribbon of the same color, but semi-transparent
    
    :args:
        x (N-by-1): positions on horizontal axis
        y (N-by-1): corresponding vertical values of the (center) line
        ups (N-by-1): upper edge of the ribbon
        downs (N-by-1): lower edge of the ribbon
        
    :returns:
        [line, patch] returns of underlying "plot" and "fill_between" function
    """
    pt1 = plot(x, y, color, **kwargs )
    pt2 = fill_between(xdat, ups, downs, color='None', facecolor=color, lw=0, alpha=alpha)
    return [pt1, pt2]


    

In [26]:

    

figure()
xdat = arange(10)/5.
ydat = xdat**2
plotband(xdat, ydat, ydat+.5, ydat-.7, linestyle='--')


    

    
Out[26]:





[[<matplotlib.lines.Line2D at 0x7f82c901fe50>],
 <matplotlib.collections.PolyCollection at 0x7f82c902a9d0>]






    

In [1]:

    

%load_ext cythonmagic


    

In [40]:

    

%%cython -lm

import numpy as np
cimport numpy as np
#from libc.math cimport sqrt # much, much faster than np.sqrt
from cpython cimport bool

def find_first(np.ndarray[np.float_t, ndim=1] data, double value):
    """
    finds the index of the first elem in data that is larger than value
    
    :args:
        data (1d numpy array): array to be searched
        value (float): value for comparison
        
    :returns:
        idx (int): the index of the first elem in data that is > than value
    """
    
    cdef int ii
    for ii in range(data.shape[0]):
        if data[ii] > value:
            return ii
    return ii
    
def find_first_sorted(np.ndarray[np.float_t, ndim=1] data, double value):
    """
    finds the index of the first elem in data that is larger than value
    it is assumed that data is sorted
    
    :args:
        data (1d numpy array): array to be searched
        value (float): value for comparison
        
    :returns:
        idx (int): the index of the first elem in data that is > than value
    """
    
    cdef int ii
    cdef bool is_larger = True
    ii = data.shape[0] - 1
    while data[ii] > value:        
        ii = ii//2
        if ii == 1:
            break
    while data[ii] > value:
        ii -= 1
        if ii == 0:
            break
    return ii


    

In [11]:

    

tst = arange(1000, dtype=float)


    

In [26]:

    

%timeit find_first(tst, 5.)


    

    




1000000 loops, best of 3: 322 ns per loop

In [19]:

    

%timeit find(tst > 500.)[0]


    

    




100000 loops, best of 3: 9.13 µs per loop

In [29]:

    

%timeit idxe = find_first_sorted(-tst, -5.)


    

    




100000 loops, best of 3: 2.36 µs per loop

In [39]:

    

idxe = find_first_sorted(tst, -2)
print idxe


    

    




-1

In [36]:

    

-tst[999] > -5


    

    
Out[36]:





False

In [ ]: