MATLAB Answers


No more plot although no errors

Asked by Peter Groh on 28 Sep 2017
Latest activity Answered by Christopher Stapels on 14 Dec 2017
My Visualizations stopped displaying anything ( no plot) - it worked for months. Even taking the template "Create a 2-D line plot" I just get the the result " _ MATLAB code ran successfully_." and no error code in the output field - but still no plot.
Is there a problem with connecting to thingspeak or what has changed?
Here the simple code from the template:
% Template MATLAB code for visualizing data from a channel as a 2D line
% plot using THINGSPEAKPLOT function.
% Prior to running this MATLAB code template, assign the channel ID to read
% data from to the 'readChannelID' variable. Also, assign the field ID
% within the channel that you want to read data from to plot.
% TODO - Replace the [] with channel ID to read data from:
readChannelID = [139311];
% TODO - Replace the [] with the Field ID to read data from:
fieldID1 = [5];
% Channel Read API Key
% If your channel is private, then enter the read API
% Key between the '' below:
readAPIKey = '';
%%Read Data %%
[data, time] = thingSpeakRead(readChannelID, 'Field', fieldID1, 'NumPoints', 30, 'ReadKey', readAPIKey);
%%Visualize Data %%
thingSpeakPlot(time, data);

  1 Comment

on 28 Sep 2017
Are data and time empty? The reason for the absence of a plot can most likely be found inside either thingSpeakRead or thingSpeakPlot.
Have a read here and here. It will greatly improve your chances of getting an answer.

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1 Answer

Answer by Christopher Stapels on 14 Dec 2017
 Accepted Answer

As of December 14, your channel has recent values in it. I think the NaN values between real values are making the plot scale unexpectedly. Try adding a LineSpec For example, plot(timeA,dataA,'ro-');


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