# Variables saved along parcel trajectories (pathlines)

**URL:** <https://vapor.discourse.group/t/variables-saved-along-parcel-trajectories-pathlines/405>\
**Category:** Uncategorized\
**Created:** [September 2, 2024, 6:21pm UTC](https://vapor.discourse.group/t/variables-saved-along-parcel-trajectories-pathlines/405 "2024-09-02T18:21:54Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![elucy](https://avatars.discourse-cdn.com/v4/letter/e/85e7bf/32.png) [@elucy](https://vapor.discourse.group/u/elucy)\
**Post date:** [September 2, 2024, 6:21pm UTC](https://vapor.discourse.group/t/variables-saved-along-parcel-trajectories-pathlines/405/1 "2024-09-02T18:21:54Z")

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In order to properly visualize variables along pathlines, does one need to change the default integration settings? Without checking the boxes in the screenshot titled “a,” the “VaporFlow” file selected in screenshot “b”

 ![b](https://global.discourse-cdn.com/free1/uploads/vapor/original/1X/bad7fbf2addc4fd56704557b89ce75b8f2401a2d.png)  
creates the following time series in screenshot “c.”  
 ![c](https://global.discourse-cdn.com/free1/uploads/vapor/original/1X/0c4cb61bb9a5b66b0c396b69f434675ed0cd65a6.png)

The stepping between values at each time step seems strange to me.

 ![a](https://global.discourse-cdn.com/free1/uploads/vapor/original/1X/9ab02f7428ecc49b6f911096dd8c15f828d46bde.png)

Any thoughts on such visualizations are much appreciated.

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**Author:** ![sam](https://avatars.discourse-cdn.com/v4/letter/s/5f9b8f/32.png) [@sam](https://vapor.discourse.group/u/sam)\
**Post date:** [September 6, 2024, 7:28pm UTC](https://vapor.discourse.group/t/variables-saved-along-parcel-trajectories-pathlines/405/2 "2024-09-06T19:28:28Z")

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Hi @elucy , could you please clarify the issue a little bit? Specifically,

1. Did you mean that the plot (in “C”) is not quite right, or that the checkboxes (in “A”) are not making sense?
2. What’s the nature of the data to result in a vertical segment on the plot in “C”? We thought that there cannot be multiple Y values with the same X value?

Thanks!  
Sam

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**Author:** ![elucy](https://avatars.discourse-cdn.com/v4/letter/e/85e7bf/32.png) [@elucy](https://vapor.discourse.group/u/elucy)\
**Post date:** [September 6, 2024, 8:38pm UTC](https://vapor.discourse.group/t/variables-saved-along-parcel-trajectories-pathlines/405/3 "2024-09-06T20:38:18Z")

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Hello!

I think the plot in ‘C’ does not look quite right to me, especially with reference to your second point. That plot should just be the stretching term in the vorticity equation along a single pathline. And more generally, I think I’m confused about the options under integration settings in ‘A.’ I couldn’t find anything about that in the documentation. Thanks so much!

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**Author:** ![sam](https://avatars.discourse-cdn.com/v4/letter/s/5f9b8f/32.png) [@sam](https://vapor.discourse.group/u/sam)\
**Post date:** [September 10, 2024, 6:24pm UTC](https://vapor.discourse.group/t/variables-saved-along-parcel-trajectories-pathlines/405/4 "2024-09-10T18:24:35Z")

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Hi @elucy , I see what you mean here. I think the best way to move forward is to provide us with a sample data set and briefly describe what you want to achieve. By doing so we can better understand your use case, and may also catch any error in the program (or provide better instructions to achieve your objectives).

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**Author:** ![elucy](https://avatars.discourse-cdn.com/v4/letter/e/85e7bf/32.png) [@elucy](https://vapor.discourse.group/u/elucy)\
**Post date:** [September 11, 2024, 3:04pm UTC](https://vapor.discourse.group/t/variables-saved-along-parcel-trajectories-pathlines/405/5 "2024-09-11T15:04:30Z")

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You can find a sample data set at /glade/u/home/elucy/trajectories/datasets1/feature1\_cm1out\_15\_00\_to\_15\_10.nc

The objective is to save a variable, such as the stretching term (‘stretch’ in the netCDF file) along pathlines, and plot those time series.

Thanks again for the help.