I am trying to get sensor data from Ubidots and plot them in a graph using
Matplotlib. The graph can then be displayed on a web server via Flask. I am
getting the following error when I run the codes:
TypeError: float() argument must be a string or a number
I think I have formatted the timestamp well and I checked questions related
to that but I don't know what's wrong with the codes. This may seem like a
duplicate of my previous [question][1] but this is another error with
updated codes so I thought I should post it as a new question.
Matplotlib-Flask.py
from flask import Flask, request, render_template
from datetime import datetime
from ubidots import ApiClient
import matplotlib.pyplot as plt
import matplotlib.dates as mdates
import matplotlib.animation as animation
from matplotlib.backends.backend_agg import FigureCanvasAgg as
FigureCanvas
from matplotlib.figure import Figure
import io
app = Flask(__name__)
//get the latest value of the ldr sensor from Ubidots
def get_records():
api = ApiClient(token='XXXXXXXXXXXXXXXXXXXXXXX')
my_variable = api.get_variable('XXXXXXXXXXXXXXXXXXXX')
ldr = my_variable.get_values(1)
return ldr
//get the latest timestamp from Ubidots
def get_times():
api = ApiClient(token='XXXXXXXXXXXXXXXXXXXXXXXX')
variable = api.get_variable('XXXXXXXXXXXXXXXXXXXXXX')
value = variable.get_values(1)[0]
timestamp = value.get('timestamp')
global t
t= mdates.epoch2num(timestamp)
return t
//render the graph with x and y values of time and sensor values
respectively and send to Flask
@app.route('/', methods=['POST'])
def my_form_post():
ldr= get_records()
time= get_time()
templateData = {
'ldr' : ldr,
'time' : t
}
return render_template('main.html', **templateData)
//Plotting the graph using Matplotlib
@app.route('/')
def plot_temp():
ldr= get_records()
ys = ldr
fig = Figure()
axis = fig.add_subplot(1,1,1)
axis.set_title("Light Intensity")
axis.set_xlabel("Time")
axis.xaxis.set_major_formatter(mdates.DateFormatter('%H:%M:%S'))
axis.grid(True)
time= get_times()
xs = time
axis.plot(xs,ys)
canvas = FigureCanvas(fig)
output = io.BytesIO()
canvas.print_png(output)
response = make_response(output.getvalue())
response.mimetype = 'image/png'
ani= animation.FuncAnimation(fig, animate, interval=3000)
return response
if __name__ == "__main__":
app.run(host='0.0.0.0', port=80, debug=True)
main.html:
<!DOCTYPE html>
<head>
<title>{{ title }}</title>
</head>
<body>
Hello, World!
The date and time on the server is: {{ time }}
</>
</body>
</html>
I used the following reference links in case that helps:
Ubidots timestamp:
http://community.ubidots.com/t/convert-timestamp-on-json/473/2
Ubidots Python API: https://github.com/ubidots/ubidots-python
Flask: http://www.mattrichardson.com/Raspberry-Pi-Flask/index.html
Matplotlib graph using Flask:
http://www.instructables.com/id/From-Data-to-Graph-a-Web-Jorney-With-Flask-and-SQL/
[1]:
https://stackoverflow.com/questions/48849227/matplotlib-getting-valueerror-invalid-literal-for-float
···
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