如何在numpy数组中找到最近的值?例子:
np.find_nearest(array, value)
如何在numpy数组中找到最近的值?例子:
np.find_nearest(array, value)
当前回答
下面是@Ari Onasafari的scipy版本,回答“在向量数组中找到最近的向量”
In [1]: from scipy import spatial
In [2]: import numpy as np
In [3]: A = np.random.random((10,2))*100
In [4]: A
Out[4]:
array([[ 68.83402637, 38.07632221],
[ 76.84704074, 24.9395109 ],
[ 16.26715795, 98.52763827],
[ 70.99411985, 67.31740151],
[ 71.72452181, 24.13516764],
[ 17.22707611, 20.65425362],
[ 43.85122458, 21.50624882],
[ 76.71987125, 44.95031274],
[ 63.77341073, 78.87417774],
[ 8.45828909, 30.18426696]])
In [5]: pt = [6, 30] # <-- the point to find
In [6]: A[spatial.KDTree(A).query(pt)[1]] # <-- the nearest point
Out[6]: array([ 8.45828909, 30.18426696])
#how it works!
In [7]: distance,index = spatial.KDTree(A).query(pt)
In [8]: distance # <-- The distances to the nearest neighbors
Out[8]: 2.4651855048258393
In [9]: index # <-- The locations of the neighbors
Out[9]: 9
#then
In [10]: A[index]
Out[10]: array([ 8.45828909, 30.18426696])
其他回答
对于那些搜索多个最接近的,修改接受的答案:
import numpy as np
def find_nearest(array, value, k):
array = np.asarray(array)
idx = np.argsort(abs(array - value))[:k]
return array[idx]
看到的: https://stackoverflow.com/a/66937734/11671779
这是在向量数组中找到最近向量的扩展。
import numpy as np
def find_nearest_vector(array, value):
idx = np.array([np.linalg.norm(x+y) for (x,y) in array-value]).argmin()
return array[idx]
A = np.random.random((10,2))*100
""" A = array([[ 34.19762933, 43.14534123],
[ 48.79558706, 47.79243283],
[ 38.42774411, 84.87155478],
[ 63.64371943, 50.7722317 ],
[ 73.56362857, 27.87895698],
[ 96.67790593, 77.76150486],
[ 68.86202147, 21.38735169],
[ 5.21796467, 59.17051276],
[ 82.92389467, 99.90387851],
[ 6.76626539, 30.50661753]])"""
pt = [6, 30]
print find_nearest_vector(A,pt)
# array([ 6.76626539, 30.50661753])
对于大型数组,@Demitri给出的(优秀)答案比目前标记为最佳的答案快得多。我从以下两个方面调整了他的精确算法:
不管输入数组是否排序,下面的函数都有效。 下面的函数返回与最接近的值对应的输入数组的索引,这有点更一般。
请注意,下面的函数还处理了一个特定的边缘情况,这将导致@Demitri编写的原始函数中的错误。否则,我的算法和他的一样。
def find_idx_nearest_val(array, value):
idx_sorted = np.argsort(array)
sorted_array = np.array(array[idx_sorted])
idx = np.searchsorted(sorted_array, value, side="left")
if idx >= len(array):
idx_nearest = idx_sorted[len(array)-1]
elif idx == 0:
idx_nearest = idx_sorted[0]
else:
if abs(value - sorted_array[idx-1]) < abs(value - sorted_array[idx]):
idx_nearest = idx_sorted[idx-1]
else:
idx_nearest = idx_sorted[idx]
return idx_nearest
如果你不想使用numpy,可以这样做:
def find_nearest(array, value):
n = [abs(i-value) for i in array]
idx = n.index(min(n))
return array[idx]
import numpy as np
def find_nearest(array, value):
array = np.asarray(array)
idx = (np.abs(array - value)).argmin()
return array[idx]
使用示例:
array = np.random.random(10)
print(array)
# [ 0.21069679 0.61290182 0.63425412 0.84635244 0.91599191 0.00213826
# 0.17104965 0.56874386 0.57319379 0.28719469]
print(find_nearest(array, value=0.5))
# 0.568743859261