Plotting time series data: same range; different #obs

[donal botkinParticipant]

I have two sets of contiguous data with different granularity that I want to plot on same X-axis range. Example: 12 hours of voltage measurements by 5 second intervals; same 12 hours of temperature by 1 minute intervals. Can be stacked ‘Y’ of course.

[dgteamModerator]

Use a Date column to specify the appropriate scale for the x-axis for each set of measurements.

For example, if you have a number column of seconds that corresponds to the number of seconds for each data point, use the gear menu to convert that to a date column and set Type = ‘Time since’ and Time in = ‘Seconds’.

Or you can create a list of seconds in the correct increment using an Expression column, where the Type is set to ‘Date’. Here is an expression that will give you 12 hours of 5 second increments.

Here are the first few entries.

You can adapt the expression for minutes. Then use the seconds and minutes columns as the x axis for each respective data set.

Here is an example using minutes and hours.

Does this help?

 

[donal botkinParticipant]

If I had a timestamp for each datum collected, there would be no problem to plot against time on the X-axis.

This problem has no timestamps, only an inference that the observations were made over the same period of time and that the frequency of observations was known, albeit different.

The old-school ‘Excel’ trick was to fake a sequence by creating a column for each series with the same start and end values but different increments. Is this possible in DataGraph?

BTW, DataGraph is the absolute BEST data management and analysis software I have ever used. Over 40 years experience. All of the majors and custom creations as well. Bravo(a)!

[dgteamModerator]

First — Thank you so much for your support 🙂

If you look at the second option presented above, I think it is basically what you were doing in excel, creating a column that you will use as the x-axis.  This article may help explain the basics:  How to Fill a Column with a Series

Here are the steps broken down for time increments  ….

1. Add a function column
2. Set Type = ‘Date’
3. Set Display = ‘ICU’
4. Enter an expression that will increment time (in seconds) using the row number (#).  In this case, ‘(#-1)*5’  will fill in, starting with zero, at intervals of 5.
5. Then you are prompted to enter ‘# of rows’.  For 12 hours, ’60/5*60*12+1′ gets the right number of rows for 12 hours.

The last two screen shots above are all manufactured data, including the time sequences, using this method.

Does that make sense?

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