streamz和rcpp.cpp:8:24: error: use of overloaded operator '[]' is ambiguous (with operand types 'Rcpp::Vector<19, PreserveStorage>::const_Proxy' (aka 'const_generic_proxy<19, PreserveStorage>') and 'int')
Rcout << some_list[1][0] << "\n";
~~~~~~~~~~~~^~
rcpp.cpp:8:24: note: built-in candidate operator[](struct SEXPREC *, long)
rcpp.cpp:8:24: note: built-in candidate operator[](const struct SEXPREC *, long)
rcpp.cpp:8:24: note: built-in candidate operator[](volatile struct SEXPREC *, long)
rcpp.cpp:8:24: note: built-in candidate operator[](const volatile struct SEXPREC *, long)
1 error generated.
软件包一起工作，为使用pandas数据帧绘制流数据提供支持。
例如，hvplot软件包具有用于创建随机流数据帧的便捷实用程序：
streamz可以使用import hvplot.streamz
from streamz.dataframe import Random
sdf = Random(interval='200ms', freq='50ms')
sdf
# Stop the streaming with: sdf.stop()
在流式图表中简单地绘制它：
hvplot是否有一种简单的方法来从预先存在的sdf.hvplot()
数据帧中流式传输数据？
例如，我想说些类似的话：
pandas然后，我可以使用先前存在的import pandas as pd
df=pd.DataFrame({'a':range(0,100),'b':range(5,105)})
sdf = StreamingDataFrame(df, interval='200ms', freq='50ms')
数据帧中的示例数据，而不必使用随机的示例数据。
答案 0 :(得分：0)
据我所知...
from streamz import Stream
from streamz.dataframe import DataFrame
from time import sleep
from datetime import datetime
#Set up a source stream
source = Stream()
#Create a sample pandas dataframe
samples = pd.DataFrame({'x':[0],'y':[0]})
#The streaming dataframe takes the source stream and sample pandas dataframe
#The sample defines the dataframe schema, maybe?
sdf = DataFrame(source, example=samples)
def stest(r):
print(datetime.now())
print(r)
#I don't recall what this does
#I think what I was looking to do was display the last 3 items...?
# ...which this doesn't appear to do!
df = sdf.window(3).full()
#This seems to set a callback on stest when a stream element appears
df.stream.sink(stest)
for i in range(5):
#pull the next item in the streaming dataframe into the stream
#We could iloc on an existing dataframe?
source.emit(pd.DataFrame({'x': [i,i,i], 'y' :[i,i,i]}))
#Pause for a short while...
sleep(2)
--------
2020-01-27 19:13:06.816315
x y
0 0 0
1 0 0
2 0 0
2020-01-27 19:13:08.824016
x y
0 1 1
1 1 1
2 1 1
2020-01-27 19:13:10.829178
x y
0 2 2
1 2 2
2 2 2
2020-01-27 19:13:12.835948
x y
0 3 3
1 3 3
2 3 3
2020-01-27 19:13:14.843432
x y
0 4 4
1 4 4
2 4 4
....
Ah ..找到了一个看起来效果更好的示例。
设置我们要流式传输的数据框：
import pandas as pd
from time import sleep
from datetime import datetime
from streamz import Stream
from streamz.dataframe import DataFrame
#Set up a dummy dataframe
ddf=pd.DataFrame({'a':range(1,5),'b':range(11,15)})
print(ddf)
---
a b
0 1 11
1 2 12
2 3 13
3 4 14
并流式传输...
#Create a stream source
source = Stream()
#Create a dataframe model for the stream
samples = pd.DataFrame({'a':[0],'b':[0]})
#Creating the streaming dataframe
sdf = DataFrame(source, example=samples)
#That window thing again...
df = sdf.window(4).full()
#FUnction to run when an item appears on the stream
def stest(r):
print(datetime.now())
print(r)
#Add the callback function to streamer
df.stream.sink(stest)
#This does stream from the dataframe
for i in range(len(ddf)):
source.emit(ddf.iloc[i])
sleep(2)
df
---
2020-01-27 19:28:05.503123
a 1
b 11
Name: 0, dtype: int64
2020-01-27 19:28:07.505536
a 1
b 11
a 2
b 12
dtype: int64
2020-01-27 19:28:09.508925
a 2
b 12
a 3
b 13
dtype: int64
2020-01-27 19:28:11.514117
a 3
b 13
a 4
b 14
dtype: int64
我还发现了另一种获取数据以流向全息图的方式：
from tornado import gen
from tornado.ioloop import PeriodicCallback
from holoviews.streams import Buffer
import holoviews as hv
hv.extension('bokeh')
import numpy as np
import pandas as pd
df = pd.DataFrame({'x':range(1000), 'y':np.sin(range(1000))})
rowcount = 0
maxrows = 1000
dfbuffer = Buffer(np.zeros((0, 2)), length=20)
@gen.coroutine
def g():
global rowcount
item = df[['x','y']].iloc[rowcount].values.tolist()
dfbuffer.send(np.array([item]))
rowcount += 1
if rowcount>=maxrows:
cbdf.stop()
#How can we get the thing to stop?
cbdf = PeriodicCallback(g, 500)
cbdf.start()
hv.DynamicMap(hv.Curve, streams=[dfbuffer]).opts(padding=0.1, width=600, color = 'green',)
然后使用cbdf.stop()停止它（只有当我尝试使用它时，这似乎才对我不起作用...）
我似乎还没有一个将streamz组件连接到图表的示例（除非holoviews在`下面使用streamz？）