Hi Dash Community,
I’m new to the Dash and Plotly ecosystem and am very impressed with the functionality. I’m trying to build a simple web dashboard. The workflow is:
- the user uploads a CSV file
- a Pandas data frame is created from the data in the file in step 1
- a bar chart is created from the data frame in step 2
The data in my CSV file looks similar to the following:
df = pd.DataFrame({'Make':['Ford', 'Ford', 'Ford', 'BMW', 'BMW', 'BMW', Mercedes', 'Mercedes', 'Mercedes'],
'Score':['88.6', '76.6', '100', '79.1', '86.8', '96.4', '97.3', '98.7', '98.5'],
'Dimension':['Speed', 'MPG', 'Styling', 'Speed', 'MPG', 'Styling', 'Speed', 'MPG', 'Styling'],
'Month':['Apr-19', 'Apr-19', 'Apr-19', 'Apr-19', 'Apr-19', 'Apr-19', 'Apr-19', 'Apr-19', 'Apr-19']})
My code is as follows:
import base64
import datetime
import io
import dash
from dash.dependencies import Input, Output, State
import dash_core_components as dcc
import dash_html_components as html
import plotly.graph_objects as go
import dash_table
import pandas as pd
app = dash.Dash()
app.layout = html.Div([
dcc.Upload(
id='upload-data',
children=html.Div([
'Drag and Drop or ',
html.A('Select Files')
]),
style={
'width': '100%',
'height': '60px',
'lineHeight': '60px',
'borderWidth': '1px',
'borderStyle': 'dashed',
'borderRadius': '5px',
'textAlign': 'center',
'margin': '10px'
},
# Allow multiple files to be uploaded
multiple=True
),
html.Div(id='output-data-upload'),
])
def parse_contents(contents, filename, date):
content_type, content_string = contents.split(',')
decoded = base64.b64decode(content_string)
try:
if 'csv' in filename:
# Assume that the user uploaded a CSV file
df = pd.read_csv(
io.StringIO(decoded.decode('utf-8')))
elif 'xls' in filename:
# Assume that the user uploaded an excel file
df = pd.read_excel(io.BytesIO(decoded))
except Exception as e:
print(e)
return html.Div([
'There was an error processing this file.'
])
return html.Div([
html.H5(filename),
html.H6(datetime.datetime.fromtimestamp(date)),
dash_table.DataTable(
data=df.to_dict('records'),
columns=[{'name': i, 'id': i} for i in df.columns]
),
html.Hr(), # horizontal line
#### How to get the x and y values DYNAMICALLY from the data frame to pass into the Bar() function? ####
dcc.Graph(
figure = go.Figure(data=[
go.Bar(name=df.columns.values[0], x=pd.unique(df['Make']), y=df['Score'], text=df['Score'], textposition='auto'),
go.Bar(name=df.columns.values[1], x=pd.unique(df['Make']), y=df['Score'], text=df['Score'], textposition='auto'),
go.Bar(name=df.columns.values[2], x=pd.unique(df['Make']), y=df['Score'], text=df['Score'], textposition='auto'),
])
),
html.Hr(),
# For debugging, display the raw contents provided by the web browser
html.Div('Raw Content'),
html.Pre(contents[0:200] + '...', style={
'whiteSpace': 'pre-wrap',
'wordBreak': 'break-all'
})
])
@app.callback(Output('output-data-upload', 'children'),
[Input('upload-data', 'contents')],
[State('upload-data', 'filename'),
State('upload-data', 'last_modified')])
def update_output(list_of_contents, list_of_names, list_of_dates):
if list_of_contents is not None:
children = [
parse_contents(c, n, d) for c, n, d in
zip(list_of_contents, list_of_names, list_of_dates)]
return children
if __name__ == '__main__':
app.run_server(debug=True)
I’m able to upload and view the contents of the CSV file. I’m able to view the data. And, I’m able to render the bar plot.
But, I can’t figure out the best way to DYNAMICALLY update the number of go.Bar() functions (these values are hard-coded in based on my advanced knowledge of 3 unique values in the “Make” column).
How do I get Dash to build the bar plot DYNAMICALLY based on the unique number of values in the Make column?
Thanks in advance for helping a newbie get this toy example working!