How do I create a bar chart?

Hi,

I'm quite new to the field of manipulating my data and can't find any examples of my goal.

I have a channel with a field (fieldMotion) where I receive data from a motionsensor where I simply write ThingSpeak.setField(3, 1) for every motion detected. I would like to create a bar chart (in a Visualization) where I sum every 1's within an hour to show amount of motions per hour for a day. Also I would like to do the same per day for a week. Could anybody please help me with a working code I could use to make this work?

Answer 1

[Christopher Stapels]

Use ThingSpeakRead to get your data, i reccomend a timetable:

channelID=12397;
data = thingSpeakRead(channelID,'Fields',[1,4],'NumPoints',3,'OutputFormat','TimeTable');
% might have to add api key for private channels

Use retime to create the sum

sumData=retime(data,'hourly','sum'); % I think daily is also possible for your second request.

plot your bar chart

bar(sumData.Timestamps,sumData.TemperatureF); 

You will probably have to change TemperatureF to the name of your field. Leave the semicolon off the first command to see the varaible names when you run it.

Then add it to the channel where you want to see it.

[Stigh Aarstein]

Hi Christopher,

This code works great to make the daily bar chart.

channelID=XXX;
readAPIKey = 'YYY';

fieldID = 3; 
oneDay = [datetime('today') datetime('now')];
data = thingSpeakRead(channelID,'Fields',fieldID,'DateRange',oneDay,'OutputFormat','TimeTable','ReadKey',readAPIKey);

sumData=retime(data,'daily','sum');
bar(sumData.Timestamps,sumData.antSpray); 

Though, I can't figure out how to work with 'datetime' to make like;

• so far this week, per day
• last week, per day
• this month, per day
• last month, per day

[Christopher Stapels]

You coud use weekday

thisWeek = [datetime('today')-days(weekday(datetime('now'))) datetime('now')];

But a better method might be to create a derived channel. You can use the timecontrol to run weekly and save a summation to the derived channel. You can also save the monthly totals in the channel. You could have your script save daily values in field1, and weekly values in fiedl 2, etc.

[Stigh Aarstein]

Thanks Christopher,

Any idea how I can format the bar (x) to show hours rather than the current view?

I would like it to show 01 02 03 .... 20 21 22 23 (24 hour format).

[Christopher Stapels]

Try

yAxisVals=0:23;
bar(yAxisVals,sumData.antSpray);