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data units

 
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samcub40i



Joined: 29 May 2017
Posts: 6

PostPosted: Mon May 29, 2017 10:25 am    Post subject: data units Reply with quote

First I want to say I really like the way datagraph is structured. While I use a mac at home, I was originally searching for a similar tool for work where we only use windows machines.

One feature that would be really helpful for engineers would be the ability to assign engineering units tagged to data columns. Then conversion to other units could be handled via some list selection in the same column rather than needing to create a conversion constant and another functional data column just for the conversion.

Taylored unit conversions would also be nice since I often come across unit relationships that are not always available in standard conversions.

Again, a wonderful piece of software with great potential.
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pjuk



Joined: 01 Jun 2017
Posts: 15
Location: London, UK

PostPosted: Thu Jun 01, 2017 8:41 am    Post subject: Reply with quote

Just started using Datagraph and this immediately seemed like a great idea. I've used Origin extensively and there is an option to scale the axis by a factor under the axes tabs, but in Datagraph it only seems possible to "scale the axis" by creating a new column and re-plotting the data.
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David
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Joined: 25 Nov 2006
Posts: 1938
Location: Chapel Hill, NC

PostPosted: Thu Jun 01, 2017 10:09 am    Post subject: Reply with quote

I am going to look into this. I've thought about units in the past, and the Extra Axis allows you to convert between units without having to scale the data.

What I'm thinking is to add a menu entry to the gear menu to add a unit scale.
When you do you get two fields one for units for the raw data and another for the result value. For example if your data is in feet and you want to draw using meters, you can do

data = feet
convert = meters

The Extra Axis does this with the Convert option and has huge number of constants defined. It even has composite units like miles/hour, km/hour, km/second etc.

I will try this out in the beta and reply to this thread when it is available.

David
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David
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Joined: 25 Nov 2006
Posts: 1938
Location: Chapel Hill, NC

PostPosted: Thu Jun 01, 2017 12:39 pm    Post subject: Reply with quote

I just uploaded a new beta with this.

You turn on the conversion through the gear menu in the standard column. I might make this more visible in the future, but right now I'm trying to avoid overwhelming the UI with options.

David
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samcub40i



Joined: 29 May 2017
Posts: 6

PostPosted: Thu Jun 01, 2017 9:48 pm    Post subject: Reply with quote

David,

Just tried the beta update, it works very nicely - thank you. (Just FYI, since I already purchased through Apple Store I am having difficulty getting beta registered - doesn't recognize email address)

Suggestions:

1) allow user to define unit conversions. For example, I see there is mph and knots, but not m/s, ft/s (or fps), etc. It would be difficult keeping up with everyones conversion needs, but perhaps individuals could add to the default library.

2) something similar could be added for expressions

3) In the same way that columns indicate if the data is a date or expression, the displayed unit could be indicated at the top of the column. This is where it would be convenient to create a drop down list of conversion units that is masked to only show compatible conversions.

4) Sometimes csv files have a second header row to define units for each column. Is it possible to allow user to right click a row and import as "input unit"?
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David
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Joined: 25 Nov 2006
Posts: 1938
Location: Chapel Hill, NC

PostPosted: Thu Jun 01, 2017 11:58 pm    Post subject: Reply with quote

To register based on the app store, you first have to request a license through the Mac App store version.

1.
m/s will work. What I actually do is that all of these constants are defined in terms of SI units. m/s is in reality 1/1 = 1, since m and s are the SI units. ft is defined as 0.30... and hr = 3600 etc. That way any combination will work, and you can even put 3ft etc It will work. If you go into Window->Show Scratch the constants are defined there as well and you can see the values. They are also listed in the manual.

2. Here I'm thinking about something slightly more ambitious, namely that you specify the return unit and the expression will look at the units of the input to figure out the conversion constants. This of course means that many expressions will not be valid, for example x+y if x is in meters and y is in seconds, but will work if x is in meters and y is in feet and be converted to the unit that is required in the output.

3. I need to think about this some more. In fact, often I feel like you really don't even need to show the data in the table (uncheck the show checkbox). This is why I'm thinking about having you either have no units and you need to know what you are doing or turn on units and the program will do the right thing or indicate clearly that it can't because you have a unit mismatch.

4. I've seen this, and the same way as right click allows you to specify that a row should be used as column titles it might make sense to allow you to set units as well. Then the units would be both data and use. This would make sense for option 2.


David
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pjuk



Joined: 01 Jun 2017
Posts: 15
Location: London, UK

PostPosted: Tue Jun 06, 2017 10:56 am    Post subject: Reply with quote

Thanks David. This works a treat, although having the option for a units option in the axis options would be great.

(edit) scrap that, I just tried this and realised you can disable drawing the numbers in the primary axis settings and use the "add extra axis" command.

On another note, any chance of having more than one header row? In some cases I might have data from another institution or lab and I typically use a second or third header row to add details or comments. Would be nice to say have access to these for the legend or units. I know for the legend you can group the columns and use the group name in the legend, but this doesn't work is you start using nested groups.
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David
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Joined: 25 Nov 2006
Posts: 1938
Location: Chapel Hill, NC

PostPosted: Thu Jun 08, 2017 1:34 am    Post subject: Reply with quote

On the more than one header row issue.

Is this primarily for labels?

One idea that I have thought about in the past is to add meta data to individual columns, similar to the unit feature that I just added. That is, you can add key-value pairs where key is a string but the value is either a number or a text. The number could be used in expressions, and be added as a property like .sum, .max etc. Maybe it should also be selectable through the token. You should also be able to extract it as a global variable just like you can now extract sums etc.

Can you give me a use case?

David
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pjuk



Joined: 01 Jun 2017
Posts: 15
Location: London, UK

PostPosted: Thu Jun 08, 2017 6:38 am    Post subject: Reply with quote

Originally labels, but now you mention it for use in an expression too. I'd prefer additional rows rather than a token as it allows for easier cut/paste or importing as well as visualisation of the value, but would be happy with either!

For example I routinely measure heating rates of samples under various experimental conditions. The additional rows could hold information such as input power, frequency, ambient temp etc... which I could then use in a fit. In fact if these values could be linked somehow to the global variables it would then allow the ability to change parameters associated with a column rather than have to look through the global list.

This might be an individual request as there might not be the need for other users to handle numerous columns to represent different datasets in a single file.
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