我们可以有使用2D
convolution的方法。
的基本步骤是:
- 作为预处理步骤,与
0s
取代NaNs
,我们需要做的输入数据窗口总和。
- 对于数据值 以及
NaNs
的掩码,获得与Scipy's convolve2d
的加窗求和。我们将使用边界元素作为零。
- 从窗口大小减去窗口计数
NaNs
以获得负责求和的有效元素的计数。
- 对于边界元素,我们会逐渐减少求和的元素。
现在,这些intervaled-summations
也可以通过Scipy's
1Duniform-filter
获得,这是相对更有效的。其他好处是,我们可以指定执行这些求和/平均的轴。
有了Scipy的2D convolution
和1D uniform filter
的混合,我们将有几种方法列在下面。
导入相关SciPy的功能 -
from scipy.signal import convolve2d as conv2
from scipy.ndimage.filters import uniform_filter1d as uniff
方法#1:
def nanmoving_mean_numpy(data, W): # data: input array, W: Window size
N = data.shape[-1]
hW = (W-1)//2
nan_mask = np.isnan(data)
data1 = np.where(nan_mask,0,data)
value_sums = conv2(data1.reshape(-1,N),np.ones((1,W)),'same', boundary='fill')
nan_sums = conv2(nan_mask.reshape(-1,N),np.ones((1,W)),'same', boundary='fill')
value_sums.shape = data.shape
nan_sums.shape = data.shape
b_sizes = hW+1+np.arange(hW) # Boundary sizes
count = np.hstack((b_sizes , W*np.ones(N-2*hW), b_sizes[::-1]))
return value_sums/(count - nan_sums)
方法2:
def nanmoving_mean_numpy_v2(data, W): # data: input array, W: Window size
N = data.shape[-1]
hW = (W-1)//2
nan_mask = np.isnan(data)
data1 = np.where(nan_mask,0,data)
value_sums = uniff(data1,size=W, axis=-1, mode='constant')*W
nan_sums = conv2(nan_mask.reshape(-1,N),np.ones((1,W)),'same', boundary='fill')
nan_sums.shape = data.shape
b_sizes = hW+1+np.arange(hW) # Boundary sizes
count = np.hstack((b_sizes , W*np.ones(N-2*hW,dtype=int), b_sizes[::-1]))
out = value_sums/(count - nan_sums)
out = np.where(np.isclose(count, nan_sums), np.nan, out)
return out
方法3:
def nanmoving_mean_numpy_v3(data, W): # data: input array, W: Window size
N = data.shape[-1]
hW = (W-1)//2
nan_mask = np.isnan(data)
data1 = np.where(nan_mask,0,data)
nan_avgs = uniff(nan_mask.astype(float),size=W, axis=-1, mode='constant')
b_sizes = hW+1+np.arange(hW) # Boundary sizes
count = np.hstack((b_sizes , W*np.ones(N-2*hW), b_sizes[::-1]))
scale = ((count/float(W)) - nan_avgs)
out = uniff(data1,size=W, axis=-1, mode='constant')/scale
out = np.where(np.isclose(scale, 0), np.nan, out)
return out
运行测试
数据集#1:
In [807]: # Create random input array and insert NaNs
...: data = np.random.randint(10,size=(20,30,60)).astype(float)
...:
...: # Add 10% NaNs across the data randomly
...: idx = np.random.choice(data.size,size=int(data.size*0.1),replace=0)
...: data.ravel()[idx] = np.nan
...:
...: W = 5 # Window size
...:
In [808]: %timeit nanmoving_mean(data,window=W,axis=2)
...: %timeit nanmoving_mean_numpy(data, W)
...: %timeit nanmoving_mean_numpy_v2(data, W)
...: %timeit nanmoving_mean_numpy_v3(data, W)
...:
10 loops, best of 3: 22.3 ms per loop
100 loops, best of 3: 3.31 ms per loop
100 loops, best of 3: 2.99 ms per loop
1000 loops, best of 3: 1.76 ms per loop
数据集#2更大的数据集]:
In [811]: # Create random input array and insert NaNs
...: data = np.random.randint(10,size=(120,130,160)).astype(float)
...:
...: # Add 10% NaNs across the data randomly
...: idx = np.random.choice(data.size,size=int(data.size*0.1),replace=0)
...: data.ravel()[idx] = np.nan
...:
In [812]: %timeit nanmoving_mean(data,window=W,axis=2)
...: %timeit nanmoving_mean_numpy(data, W)
...: %timeit nanmoving_mean_numpy_v2(data, W)
...: %timeit nanmoving_mean_numpy_v3(data, W)
...:
1 loops, best of 3: 796 ms per loop
1 loops, best of 3: 486 ms per loop
1 loops, best of 3: 275 ms per loop
10 loops, best of 3: 161 ms per loop
我不哪里看apply_along_axis的代码,但它如何构造我和ind? –
@ShichuZhu如果你正在寻找性能,'apply_along_axis'将无济于事。 – Divakar
@Divakar如果基本函数只处理1D,那么循环遍历所有其他维度是唯一的方法。除非修改基本函数以包含向量化操作,我猜? –