我有一个包含时间，纬度，经度，海拔，速度的数据框，我正在使用它来减少基于公差的数据集以平滑纬度/经度对。它工作正常，但是当我尝试将平滑的简化版本的数据点（lat，lon）与具有Time，Elevation，元素的原始数据帧匹配时，当数据点> 1时，它需要太长时间。 500。
基本上我正在做的是循环原始数据集并查找匹配对，记录索引直到它们全部匹配。我正在使用“last_find”变量来加快搜索速度，因为这些点几乎总是连续的，并且没有理由从头开始重新搜索。 FWIW，我从来没有看到它需要回到（last_find = 0）我的测试数据集上的完整数据帧扫描，这是基于数据的顺序线性和平滑方法有意义的。
lon = pd.Series(pd.Series(simplified_line.coords.xy)[1])
lat = pd.Series(pd.Series(simplified_line.coords.xy)[0])
si = pd.DataFrame({'Longitude': lon, 'Latitude': lat})
si.tail()
si['df_index'] = None
pd.options.mode.chained_assignment = None # default='warn', suppress warning during copying dataframe
last_find = 0 # assume data is sequential and and start search at last point found to reduce iterations
for si_i, si_row in si.iterrows():
si_coords = (si_row['Latitude'], si_row['Longitude'])
found = False
for df_i, df_row in islice(track.iterrows(), last_find, None):
if si_coords == (df_row['Latitude'], df_row['Longitude']):
si['df_index'][si_i] = df_i
last_find = df_i
found = True
break
if not found:
last_find = 0
# Rescanning full dataset for match
for df_i, df_row in islice(track.iterrows(), last_find, None):
if si_coords == (df_row['Latitude'], df_row['Longitude']):
si['df_index'][si_i] = df_i
last_find = df_i
break
rs = track.loc[si['df_index'].dropna()]
将数据框重建为“rs”的过程非常缓慢。 （仅需500分即可获得22秒）。有没有更好的方法来进行这种类型的匹配以减少原始数据帧大小？
以下是检查的完整示例：
import pandas as pd
from pandas import DataFrame
from shapely.geometry import LineString
from time import time
from itertools import islice
import datetime
class RDP:
def __init__(self, tracks, tolerance=0.000002):
self.df = tracks
self.tolerance = tolerance
return
def smooth(self):
"""
Smooths list of data frames
:return: list of smoothed data frames
"""
results = []
start_time = time()
for track in self.df:
coordinates = track.as_matrix(columns=['Latitude', 'Longitude'])
line = LineString(coordinates)
# If preserve topology is set to False, the method will use the Ramer-Douglas-Peucker algorithm
simplified_line = line.simplify(self.tolerance, preserve_topology=False)
lon = pd.Series(pd.Series(simplified_line.coords.xy)[1])
lat = pd.Series(pd.Series(simplified_line.coords.xy)[0])
si = pd.DataFrame({'Longitude': lon, 'Latitude': lat})
si.tail()
si['df_index'] = None
pd.options.mode.chained_assignment = None # default='warn', suppress warning during copying dataframe
last_find = 0 # assume data is sequential and and start search at last point found to reduce iterations
for si_i, si_row in si.iterrows():
si_coords = (si_row['Latitude'], si_row['Longitude'])
found = False
for df_i, df_row in islice(track.iterrows(), last_find, None):
if si_coords == (df_row['Latitude'], df_row['Longitude']):
si['df_index'][si_i] = df_i
last_find = df_i
found = True
break
if not found:
last_find = 0
# Rescanning full dataset for match
for df_i, df_row in islice(track.iterrows(), last_find, None):
if si_coords == (df_row['Latitude'], df_row['Longitude']):
si['df_index'][si_i] = df_i
last_find = df_i
break
rs = track.loc[si['df_index'].dropna()]
results.append(rs)
print('process took %s seconds' % round(time() - start_time, 2))
return results
if __name__ == "__main__":
data = [[-155.05156, 19.73201, 23.0, datetime.datetime(2017, 12, 28, 17, 50, 9), None, 0],
[-155.05156, 19.73201, 23.0, datetime.datetime(2017, 12, 28, 17, 50, 10), 0.0, 0.0],
[-155.05156, 19.73201, 23.0, datetime.datetime(2017, 12, 28, 17, 50, 11), 1.8244950963755258, 0.0],
[-155.05157, 19.73202, 22.0, datetime.datetime(2017, 12, 28, 17, 50, 12), 1.4678475295952227,
1.527543187532957],
[-155.05157, 19.73203, 22.0, datetime.datetime(2017, 12, 28, 17, 50, 13), 1.11120000035271,
1.1122983328025196],
[-155.05157, 19.73203, 22.0, datetime.datetime(2017, 12, 28, 17, 50, 14), 2.3687194876712123, 0.0],
[-155.05159, 19.73204, 22.0, datetime.datetime(2017, 12, 28, 17, 50, 15), 1.7399596859879076,
2.3710607190787623],
[-155.05159, 19.73205, 22.0, datetime.datetime(2017, 12, 28, 17, 50, 16), 1.7399596281612155,
1.112298332448747],
[-155.05161, 19.73206, 22.0, datetime.datetime(2017, 12, 28, 17, 50, 17), 1.7399595703344959,
2.3710604875433656],
[-155.05161, 19.73207, 22.0, datetime.datetime(2017, 12, 28, 17, 50, 18), 1.7399595111950648,
1.112298332448747],
[-155.05163, 19.73208, 22.0, datetime.datetime(2017, 12, 28, 17, 50, 19), 2.096606870194645,
2.3710602536550747],
[-155.05164, 19.73209, 23.0, datetime.datetime(2017, 12, 28, 17, 50, 20), 1.6752646424182498,
1.527542875149723],
[-155.05165, 19.7321, 23.0, datetime.datetime(2017, 12, 28, 17, 50, 21), 2.289051665826317,
1.5275428299682154],
[-155.05167, 19.73212, 23.0, datetime.datetime(2017, 12, 28, 17, 50, 22), 2.754150510219822,
3.055085523596321],
[-155.05168, 19.73214, 23.0, datetime.datetime(2017, 12, 28, 17, 50, 23), 2.4562322562443732,
2.458660072750598],
[-155.05169, 19.73216, 23.0, datetime.datetime(2017, 12, 28, 17, 50, 24), 2.4124750922364004,
2.458660017743196],
[-155.05171, 19.73217, 23.0, datetime.datetime(2017, 12, 28, 17, 50, 25), 2.9312779133573135,
2.3710592140947706],
[-155.05172, 19.7322, 23.0, datetime.datetime(2017, 12, 28, 17, 50, 26), 2.9312777104723176,
3.497291307909982],
[-155.05174, 19.73221, 23.0, datetime.datetime(2017, 12, 28, 17, 50, 27), 2.7103926533029608,
2.3710587533735854],
[-155.05176, 19.73223, 23.0, datetime.datetime(2017, 12, 28, 17, 50, 28), 2.7541498631496495,
3.0550845355246805],
[-155.05177, 19.73225, 23.0, datetime.datetime(2017, 12, 28, 17, 50, 29), 3.214644630731547,
2.4586597654103666],
[-155.0518, 19.73227, 22.0, datetime.datetime(2017, 12, 28, 17, 50, 30), 3.272104136727811,
3.8489512292988133],
[-155.05182, 19.73228, 23.0, datetime.datetime(2017, 12, 28, 17, 50, 31), 2.4699338807004922,
2.3710579406395524],
[-155.05184, 19.73229, 23.0, datetime.datetime(2017, 12, 28, 17, 50, 32), 2.710391831502253,
2.3710578250365275],
[-155.05186, 19.73231, 23.0, datetime.datetime(2017, 12, 28, 17, 50, 33), 2.571984173054396,
3.055083816479077],
[-155.05188, 19.73231, 23.0, datetime.datetime(2017, 12, 28, 17, 50, 34), 2.2303087951040954,
2.0939690200246193],
[-155.0519, 19.73232, 23.0, datetime.datetime(2017, 12, 28, 17, 50, 35), 2.412473942713288,
2.371057475376574],
[-155.05191, 19.73234, 23.0, datetime.datetime(2017, 12, 28, 17, 50, 36), 2.892513413572397,
2.458659515345401],
[-155.05194, 19.73235, 23.0, datetime.datetime(2017, 12, 28, 17, 50, 37), 3.1904307936770424,
3.3320852845152014],
[-155.05196, 19.73237, 23.0, datetime.datetime(2017, 12, 28, 17, 50, 38), 3.190430517344615,
3.0550832771287606],
[-155.05199, 19.73238, 23.0, datetime.datetime(2017, 12, 28, 17, 50, 39), 3.1904303798788662,
3.332084723430405],
[-155.05201, 19.7324, 23.0, datetime.datetime(2017, 12, 28, 17, 50, 40), 2.710390701811524,
3.055083009665372],
[-155.05203, 19.73241, 23.0, datetime.datetime(2017, 12, 28, 17, 50, 41), 2.3687150928988454,
2.3710564358044426],
[-155.05205, 19.73242, 23.0, datetime.datetime(2017, 12, 28, 17, 50, 42), 2.4699323240615967,
2.371056320034746],
[-155.05207, 19.73243, 22.0, datetime.datetime(2017, 12, 28, 17, 50, 43), 2.4699322129590935,
2.371056201746366],
[-155.05209, 19.73244, 22.0, datetime.datetime(2017, 12, 28, 17, 50, 44), 3.1708845562819272,
2.3710560884951897],
[-155.05212, 19.73246, 23.0, datetime.datetime(2017, 12, 28, 17, 50, 45), 3.1708842854814536,
3.8489481826678027],
[-155.05214, 19.73247, 23.0, datetime.datetime(2017, 12, 28, 17, 50, 46), 2.710389981744121,
2.371055741019484],
[-155.05216, 19.73249, 23.0, datetime.datetime(2017, 12, 28, 17, 50, 47), 2.710389776420281,
3.0550821973706315],
[-155.05218, 19.7325, 23.0, datetime.datetime(2017, 12, 28, 17, 50, 48), 2.710389674730764,
2.3710553940411665],
[-155.0522, 19.73252, 23.0, datetime.datetime(2017, 12, 28, 17, 50, 49), 3.0520651178491267,
3.055081929390566],
[-155.05222, 19.73254, 23.0, datetime.datetime(2017, 12, 28, 17, 50, 50), 2.7103892638045273,
3.0550817499490517],
[-155.05224, 19.73255, 23.0, datetime.datetime(2017, 12, 28, 17, 50, 51), 2.710389160077225,
2.371054817376382],
[-155.05226, 19.73257, 23.0, datetime.datetime(2017, 12, 28, 17, 50, 52), 2.7103889546600244,
3.0550814785741593],
[-155.05228, 19.73258, 23.0, datetime.datetime(2017, 12, 28, 17, 50, 53), 3.1069293021008604,
2.3710544675462026],
[-155.05231, 19.7326, 23.0, datetime.datetime(2017, 12, 28, 17, 50, 54), 2.6855886784059737,
3.8489459341931775],
[-155.05232, 19.73261, 23.0, datetime.datetime(2017, 12, 28, 17, 50, 55), 2.2890482314811806,
1.5275405390797137],
[-155.05234, 19.73263, 23.0, datetime.datetime(2017, 12, 28, 17, 50, 56), 3.0520641294586754,
3.055080939475094],
[-155.05236, 19.73265, 23.0, datetime.datetime(2017, 12, 28, 17, 50, 57), 3.052063950954796,
3.0550807613433832],
[-155.05238, 19.73267, 23.0, datetime.datetime(2017, 12, 28, 17, 50, 58), 3.131887830893072,
3.0550805819008096],
[-155.0524, 19.73269, 22.0, datetime.datetime(2017, 12, 28, 17, 50, 59), 2.79021178709455,
3.0550804024580738],
[-155.05242, 19.7327, 22.0, datetime.datetime(2017, 12, 28, 17, 51), 2.710387619443569, 2.371053080813694],
[-155.05244, 19.73272, 22.0, datetime.datetime(2017, 12, 28, 17, 51, 1), 2.7103874140249378,
3.0550801308237463],
[-155.05246, 19.73273, 22.0, datetime.datetime(2017, 12, 28, 17, 51, 2), 2.790211385044462,
2.3710527309810545],
[-155.05248, 19.73275, 23.0, datetime.datetime(2017, 12, 28, 17, 51, 3), 2.7902111840874317,
3.0550798630984697],
[-155.0525, 19.73276, 23.0, datetime.datetime(2017, 12, 28, 17, 51, 4), 2.7103870033308333,
2.3710523836665467],
[-155.05252, 19.73278, 23.0, datetime.datetime(2017, 12, 28, 17, 51, 5), 3.4486025267361144,
3.0550795919786187],
[-155.05255, 19.7328, 23.0, datetime.datetime(2017, 12, 28, 17, 51, 6), 2.685586626408571,
3.848942726844205],
[-155.05256, 19.73281, 23.0, datetime.datetime(2017, 12, 28, 17, 51, 7), 2.3688709766335045,
1.5275396387506783],
[-155.05258, 19.73283, 22.0, datetime.datetime(2017, 12, 28, 17, 51, 8), 2.790210380257448,
3.055079144293523],
[-155.0526, 19.73284, 22.0, datetime.datetime(2017, 12, 28, 17, 51, 9), 2.7902102788103615,
2.37105145984478],
[-155.05262, 19.73286, 23.0, datetime.datetime(2017, 12, 28, 17, 51, 10), 3.211710268550555,
3.0550788729150917],
[-155.05264, 19.73288, 22.0, datetime.datetime(2017, 12, 28, 17, 51, 11), 3.1318859927435865,
3.0550786952967113],
[-155.05266, 19.7329, 22.0, datetime.datetime(2017, 12, 28, 17, 51, 12), 2.71038556626744,
3.0550785153370557],
[-155.05268, 19.73291, 22.0, datetime.datetime(2017, 12, 28, 17, 51, 13), 2.3687093086562108,
2.3710506470866193],
[-155.0527, 19.73292, 22.0, datetime.datetime(2017, 12, 28, 17, 51, 14), 2.469926768769237,
2.3710505291274866],
[-155.05272, 19.73293, 23.0, datetime.datetime(2017, 12, 28, 17, 51, 15), 3.272095501921749,
2.3710504155416987],
[-155.05275, 19.73295, 22.0, datetime.datetime(2017, 12, 28, 17, 51, 16), 3.170877650790823,
3.8489403198357444],
[-155.05277, 19.73296, 22.0, datetime.datetime(2017, 12, 28, 17, 51, 17), 2.3687087304575547,
2.371050068389868],
[-155.05279, 19.73297, 22.0, datetime.datetime(2017, 12, 28, 17, 51, 18), 2.3687086147991403,
2.3710499502645015],
[-155.05281, 19.73298, 22.0, datetime.datetime(2017, 12, 28, 17, 51, 19), 2.790208873068198,
2.3710498368443993],
[-155.05283, 19.733, 23.0, datetime.datetime(2017, 12, 28, 17, 51, 20), 2.7902086721088404,
3.0550776168243536],
[-155.05285, 19.73301, 23.0, datetime.datetime(2017, 12, 28, 17, 51, 21), 2.3687081533850103,
2.3710494917124847],
[-155.05287, 19.73302, 23.0, datetime.datetime(2017, 12, 28, 17, 51, 22), 2.368708036413647,
2.3710493735868456],
[-155.05289, 19.73303, 23.0, datetime.datetime(2017, 12, 28, 17, 51, 23), 2.71038422971785,
2.3710492556271126],
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3.055077167566475],
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2.4586574769885563],
[-155.05294, 19.73308, 23.0, datetime.datetime(2017, 12, 28, 17, 51, 26), 2.368707343773043,
2.371048681300471],
[-155.05296, 19.73309, 23.0, datetime.datetime(2017, 12, 28, 17, 51, 27), 2.7103836137458464,
2.3710485633404104],
[-155.05298, 19.73311, 23.0, datetime.datetime(2017, 12, 28, 17, 51, 28), 2.7103834083234952,
3.0550766266297775],
[-155.053, 19.73312, 23.0, datetime.datetime(2017, 12, 28, 17, 51, 29), 2.710383306631016,
2.3710482158540307],
[-155.05302, 19.73314, 23.0, datetime.datetime(2017, 12, 28, 17, 51, 30), 3.190419933693602,
3.0550763588997274],
[-155.05305, 19.73315, 23.0, datetime.datetime(2017, 12, 28, 17, 51, 31), 2.8487433306642,
3.332070455791797],
[-155.05307, 19.73316, 23.0, datetime.datetime(2017, 12, 28, 17, 51, 32), 2.710382894565474,
2.371047750738638],
[-155.05309, 19.73318, 23.0, datetime.datetime(2017, 12, 28, 17, 51, 33), 2.811600384514776,
3.055075999491225],
[-155.05311, 19.73319, 22.0, datetime.datetime(2017, 12, 28, 17, 51, 34), 2.5711414689310477,
2.3710474054378037],
[-155.05313, 19.7332, 23.0, datetime.datetime(2017, 12, 28, 17, 51, 35), 2.811600187179107,
2.371047289829799],
[-155.05315, 19.73322, 23.0, datetime.datetime(2017, 12, 28, 17, 51, 36), 3.190418832907143,
3.055075638256173],
[-155.05318, 19.73323, 23.0, datetime.datetime(2017, 12, 28, 17, 51, 37), 2.9903853616785745,
3.3320689728999744],
[-155.05319, 19.73325, 22.0, datetime.datetime(2017, 12, 28, 17, 51, 38), 2.5103487005418743,
2.4586569745708617],
[-155.05321, 19.73326, 22.0, datetime.datetime(2017, 12, 28, 17, 51, 39), 2.710381868668547,
2.3710465975375103],
[-155.05323, 19.73328, 22.0, datetime.datetime(2017, 12, 28, 17, 51, 40), 2.7103816619319017,
3.0550751009671164],
[-155.05325, 19.73329, 22.0, datetime.datetime(2017, 12, 28, 17, 51, 41), 2.3687049136083917,
2.3710462453430305],
[-155.05327, 19.7333, 22.0, datetime.datetime(2017, 12, 28, 17, 51, 42), 2.3687047992608443,
2.371046131921171],
[-155.05329, 19.73331, 22.0, datetime.datetime(2017, 12, 28, 17, 51, 43), 2.710381355108257,
2.3710460163125644],
[-155.05331, 19.73333, 22.0, datetime.datetime(2017, 12, 28, 17, 51, 44), 2.7103811483711353,
3.0550746517035354],
[-155.05333, 19.73334, 22.0, datetime.datetime(2017, 12, 28, 17, 51, 45), 2.368704335399346,
2.371045666469919],
[-155.05335, 19.73335, 22.0, datetime.datetime(2017, 12, 28, 17, 51, 46), 3.1069186773136934,
2.3710455533797066],
[-155.05338, 19.73337, 22.0, datetime.datetime(2017, 12, 28, 17, 51, 47), 2.685580778436882,
3.8489335801226137],
[-155.05339, 19.73338, 22.0, datetime.datetime(2017, 12, 28, 17, 51, 48), 2.427402283410334,
1.5275370795403593]]
columns = ['Longitude', 'Latitude', 'Altitude', 'Time', 'Speed',
'Distance']
df = list()
df.append(DataFrame(data, columns=columns))
rdp = RDP(df)
print(rdp.smooth())
答案 0 :(得分：1)
最难的部分是了解你的要求。这相当于从第一个for循环开始的所有代码。
rs = si.merge( track, on = ["Latitude", "Longitude"] )
您基本上只是基于2列合并两个数据帧。此合并默认为内部合并，这将只保留两个行中的匹配行。