The MATLAB Analysis and MATLAB Visualizations apps in ThingSpeak™ let you pick from a selection of code templates as a starting point for building your own project. This example demonstrates how to read data, identify certain elements, and display the results. The example uses data from ThingSpeak channel 12397, which collects weather data from an Arduino® based weather station in Natick, MA.
To calculate the maximum and minimum daily temperatures from the Natick weather station, write a MATLAB® script using the code template provided.
Navigate to the Apps tab in ThingSpeak, and select MATLAB Analysis. Click New, choose Calculate high and low temperatures, and click Create.
The MATLAB Code field is prepopulated with code to calculate the maximum and minimum temperatures over the past 24 hours.
Set the variables for communicating with ThingSpeak. The
readChannelID is the channel ID for the
public channel that collects data from the weather station. The
temperatureFieldID is the field in the channel that
contains temperature values. Assign a value to
only if you are reading data from your own private channel instead of the
weather station channel.
readChannelID = 12397; temperatureFieldID = 4; readAPIKey = '';
Read temperature values from the past 24 hours using the
[tempF,timeStamp] = thingSpeakRead(readChannelID,'Fields',temperatureFieldID,'numDays',1,'ReadKey',readAPIKey);
[maxTempF,maxTempIndex] = max(tempF); [minTempF,minTempIndex] = min(tempF); timeMaxTemp = timeStamp(maxTempIndex); timeMinTemp = timeStamp(minTempIndex); display(maxTempF,'Maximum Temperature for the past 24 hours is'); display(minTempF,'Minimum Temperature for the past 24 hours is');
Execute your code by clicking Save and Run. The Output field displays your results.
Store your maximum or minimum temperature calculation result by writing it to a private channel. To create a ThingSpeak channel, go to the Channels tab, and select My Channels. Click New Channel. Select the corresponding check box, and enter these channel setting values:
Click Save Channel.
In the MATLAB Code field, set the variables for writing to your
private channel. Replace the given values for
writeAPIKey with your values. You can find the channel ID
and API Key under the Channel Info panel on the right side
% Replace the  with channel ID to write data to: writeChannelID = ; % Enter the Write API Key between the '' below: writeAPIKey = '';
Write the maximum temperature reading to your channel. To save the minimum
temperature value, change
Execute your code by clicking Save and Run. The chart in your ThingSpeak channel is populated with a single point, representing the maximum temperature reading at the time when it was recorded. You can access your channel by clicking the channel link in the Channel Info panel on the right side of the page.