为什么我的散点图无法显示带有多个下拉选项的图？

Question

我正在使用破折号和绘图来构建一个简单的python仪表板。我也是python的新手（可能很明显！），我为任何/所有更正感到高兴。我想从一个预定的CSV文件中绘制一个时间序列的数据。我添加了一个下拉选择框，我希望使用该下拉框来绘制多个不同的列。

样本数据：

"TOA5","HE605_RV50_GAF","CR6","7225","CR6.Std.07","CPU:BiSP5_GAF_v2d.CR6","51755","SensorStats"
"TIMESTAMP","RECORD","BattV_Min","BattV_Avg","PTemp_C_Avg","SensorRel_Min(1)","SensorRel_Min(2)","SensorRel_Min(3)","SensorRel_Min(4)","SensorRel_Min(5)","SensorRel_Max(1)","SensorRel_Max(2)","SensorRel_Max(3)","SensorRel_Max(4)","SensorRel_Max(5)"
"TS","RN","Volts","Volts","Deg C","","","","","","","","","",""
"","","Min","Avg","Avg","Min","Min","Min","Min","Min","Max","Max","Max","Max","Max"
"2019-09-30 11:15:00",0,12.68219,12.74209,"NAN","NAN","NAN","NAN","NAN","NAN","NAN","NAN","NAN","NAN","NAN"
"2019-09-30 11:30:00",1,12.68466,12.73777,31.26331,-2.498894,-2.38887,-8.497528,-2.963989,-20.42339,41.51585,28.41309,88.98283,27.27819,17.98986
"2019-09-30 11:45:00",2,12.69364,12.74584,31.43891,-3.490456,-2.856804,-8.770081,-3.879868,-22.69171,42.27676,30.53723,89.47752,34.25191,23.92586
"2019-09-30 12:00:00",3,12.69078,12.74522,31.38461,-3.290047,-2.973389,-8.69928,-3.295074,-21.88254,42.72508,29.91062,83.36012,27.9931,22.6571
"2019-09-30 12:15:00",4,12.6914,12.74376,31.2449,-2.899231,-2.392128,-10.01413,-2.996033,-23.22171,42.97162,29.20943,106.1204,35.93995,41.74426

我的python（3.7）代码是：

import dash
import dash_core_components as dcc
import dash_html_components as html
from dash.dependencies import Input, Output

import pandas as pd
import plotly.graph_objects as go

# Load external stylesheets
external_stylesheets = ['https://codepen.io/chriddyp/pen/bWLwgP.css']
app = dash.Dash(__name__, external_stylesheets=external_stylesheets)

# Load external datasets
df = pd.read_csv('../SampleData/test_data.dat', skiprows=3, na_values='NAN')
df.columns=["TIMESTAMP","RECORD","BattV_Min","BattV_Avg","PTemp_C_Avg","SensorRel_Min(1)","SensorRel_Min(2)","SensorRel_Min(3)","SensorRel_Min(4)","SensorRel_Min(5)","SensorRel_Max(1)","SensorRel_Max(2)","SensorRel_Max(3)","SensorRel_Max(4)","SensorRel_Max(5)"]

# define dropdown options
opts=[{'label': k, 'value': k} for k in list(df.columns.values)[1:]]


# create plotly figures
fig2=go.Figure()

# Create a Dash layout
app.layout = html.Div(children=[
    html.H1(children='Testing dashboard v01'),

    html.Div(children='''
        Select variable to plot below.
    '''),

    html.Div(children='''
        Select variables to add to plot below.
    '''),

    dcc.Dropdown(
        id='multiVariableDropdown',
        options=opts,
        value='RECORD',
        multi=True
    ),

    dcc.Graph(
        id='plot2'
    )  
])

# Add callback functions
## For plot 2
@app.callback(Output('plot2', 'figure'),
             [Input('multiVariableDropdown', 'value')])
def update_graph(selectedVariable2):
    trace_finalPlot2 = go.Scatter(
                            x=df['TIMESTAMP'], 
                            y=df[selectedVariable2], 
                            name=str(selectedVariable2))
    fig2 = go.Figure(data=trace_finalPlot2)
    return fig2


if __name__ == '__main__':
    app.run_server(debug=True)

绘图的初始渲染看起来不错，因为这是在运行python3 app.py之后出现的外观：

但是一旦我从多选下拉列表中添加了要绘制的另一列，原始数据就会消失，它只会绘制一个点：

不幸的是，它没有返回任何错误数据，因此调试时遇到了麻烦。任何提示/提示表示赞赏。

Answer 1

问题是，下拉列表返回多个变量的列表（如您设置的multi=True），而回调仅设计为绘制一个变量。

为了绘制多个变量，您需要遍历选定的变量列表（即，通过代码中的selectedVariable2），并将相应的迹线添加到图中。

[您还应确保下拉列表使用列表而不是字符串进行初始化（即，您应将value="RECORD"替换为value=["RECORD"]。

我在下面提供了一个示例。

import pandas as pd
import dash
import dash_core_components as dcc
import dash_html_components as html
from dash.dependencies import Input, Output
import plotly.graph_objects as go

# Load external stylesheets
external_stylesheets = ['https://codepen.io/chriddyp/pen/bWLwgP.css']
app = dash.Dash(__name__, external_stylesheets=external_stylesheets)

# Create a sample dataset
df = pd.DataFrame({"TIMESTAMP": ["2019-09-30 11:15:00", "2019-09-30 11:30:00", "2019-09-30 11:45:00", "2019-09-30 12:00:00", "2019-09-30 12:15:00"],
                   "RECORD": [0, 1, 2, 3, 4],
                   "SensorRel_Min(2)": [12.68219, 12.68466, 12.69364, 12.69078, 12.6914],
                   "SensorRel_Min(3)": [14.74209, 13.73777, 10.74584, 9.74522, 16.74376]})

# Define dropdown options
opts = [{'label': k, 'value': k} for k in list(df.columns.values)[1:]]

# Create a Dash layout
app.layout = html.Div(children=[

    html.H1(children='Testing dashboard v01'),

    html.Div(children='''
        Select variable to plot below.
    '''),

    html.Div(children='''
        Select variables to add to plot below.
    '''),

    dcc.Dropdown(
        id='multiVariableDropdown',
        options=opts,
        value=['RECORD'],
        multi=True
    ),

    dcc.Graph(
        id='plot2'
    )

])

# Add callback functions
## For plot 2
@app.callback(Output('plot2', 'figure'),
             [Input('multiVariableDropdown', 'value')])
def update_graph(selectedVariable2):

    traces = []

    for var in selectedVariable2:

        traces.append(go.Scatter(x=df['TIMESTAMP'],
                                 y=df[var],
                                 name=var))

    fig2 = go.Figure(data=traces)

    return fig2

if __name__ == '__main__':
    app.run_server(debug=True)