# Failed to initialize derived coord variable **URL:** \ **Category:** Uncategorized\ **Created:** [August 24, 2021, 2:10pm UTC](https://vapor.discourse.group/t/failed-to-initialize-derived-coord-variable/112 "2021-08-24T14:10:00Z")\ **Posts on this page:** 11\ **Page:** 1
**Author:** ![yoghurt](https://avatars.discourse-cdn.com/v4/letter/y/ad7895/32.png) [@yoghurt](https://vapor.discourse.group/u/yoghurt)\ **Post date:** [August 24, 2021, 2:10pm UTC](https://vapor.discourse.group/t/failed-to-initialize-derived-coord-variable/112/1 "2021-08-24T14:10:00Z")
Dear all, I want to draw the flow, but when I chose the flow renderer, vapor threw an error. > Error performing paint event > Update deltaT failed! > One of the selected volume dimension is zero! It seems that this error is because my file only has one moment. Then I montage the files with different time using CDO, while the file can’t be imported. The error is > Failure to open data set of type “cf” > Failed to get time coordinates > Failed to initialize derived coord variable > Can’t read time variable > Invalid time step: 1 This is the metadata of combined file. [https://drive.google.com/file/d/1yLgJCdn1wttZG8\_\_aSJ0Cb71qPepg1n7/view?usp=sharing](https://drive.google.com/file/d/1yLgJCdn1wttZG8__aSJ0Cb71qPepg1n7/view?usp=sharing) I have carefully read the instructions for netCDF-CF and checked the difference of metadata between single file and combined file, still don’t identify what went wrong. Is there anybody here who has met this error and perhaps knows a fix to the issue? Sincerely, Yoghurt ---
**Author:** ![clyne](https://avatars.discourse-cdn.com/v4/letter/c/b9e5f3/32.png) [@clyne](https://vapor.discourse.group/u/clyne)\ **Post date:** [August 26, 2021, 8:05pm UTC](https://vapor.discourse.group/t/failed-to-initialize-derived-coord-variable/112/2 "2021-08-26T20:05:00Z")
I don’t see anything obviously wrong in the metadata. Can you share the file itself? ---
**Author:** ![yoghurt](https://avatars.discourse-cdn.com/v4/letter/y/ad7895/32.png) [@yoghurt](https://vapor.discourse.group/u/yoghurt)\ **Post date:** [August 27, 2021, 8:12am UTC](https://vapor.discourse.group/t/failed-to-initialize-derived-coord-variable/112/3 "2021-08-27T08:12:08Z")
(post deleted by author) ---
**Author:** ![yoghurt](https://avatars.discourse-cdn.com/v4/letter/y/ad7895/32.png) [@yoghurt](https://vapor.discourse.group/u/yoghurt)\ **Post date:** [August 31, 2021, 12:08am UTC](https://vapor.discourse.group/t/failed-to-initialize-derived-coord-variable/112/4 "2021-08-31T00:08:25Z")
I have solved the problem of the file not opening, but it still reports > Error performing paint event > Update deltaT failed! > One of the selected volume dimension is zero! ---
**Author:** ![clyne](https://avatars.discourse-cdn.com/v4/letter/c/b9e5f3/32.png) [@clyne](https://vapor.discourse.group/u/clyne)\ **Post date:** [August 31, 2021, 1:11am UTC](https://vapor.discourse.group/t/failed-to-initialize-derived-coord-variable/112/5 "2021-08-31T01:11:00Z")
Can you dump out the value of the ‘time’ variable? E.g. ncdump -v time your\_file.nc ---
**Author:** ![yoghurt](https://avatars.discourse-cdn.com/v4/letter/y/ad7895/32.png) [@yoghurt](https://vapor.discourse.group/u/yoghurt)\ **Post date:** [August 31, 2021, 1:20am UTC](https://vapor.discourse.group/t/failed-to-initialize-derived-coord-variable/112/6 "2021-08-31T01:20:56Z")
It shows time = 135655.333333333, 135655.35, 135655.366666667, 135655.383333333, 135655.4 ---
**Author:** ![clyne](https://avatars.discourse-cdn.com/v4/letter/c/b9e5f3/32.png) [@clyne](https://vapor.discourse.group/u/clyne)\ **Post date:** [August 31, 2021, 1:47am UTC](https://vapor.discourse.group/t/failed-to-initialize-derived-coord-variable/112/7 "2021-08-31T01:47:06Z")
There is probably not enough precision internally to represent changes of 1/100th of a second. Can you try changing your time unit from “hours since 2001-01-01 00:00:00” to “hours” and only use the digits to the right of the decimal point. E.g. 0.33 0.35 0.36 0.38 ---
**Author:** ![yoghurt](https://avatars.discourse-cdn.com/v4/letter/y/ad7895/32.png) [@yoghurt](https://vapor.discourse.group/u/yoghurt)\ **Post date:** [August 31, 2021, 3:23am UTC](https://vapor.discourse.group/t/failed-to-initialize-derived-coord-variable/112/8 "2021-08-31T03:23:13Z")
In fact, the time resolution of my file is second. I just experiment with the above data. Therefore, I have changed the time unit to “second since 2016-01-01 00:00:00”. Now the time = 15060000, 15060060, 15060120, 15060180, 15060240 But it still reports the same error. This is the new file, [uvw\_2016-06-23\_07\_20\_24.nc - Google Drive](https://drive.google.com/file/d/1NTooXgBsbhSXmaDY6Hk_6bIrsBPHpt7T/view?usp=sharing) ---
**Author:** ![yoghurt](https://avatars.discourse-cdn.com/v4/letter/y/ad7895/32.png) [@yoghurt](https://vapor.discourse.group/u/yoghurt)\ **Post date:** [August 31, 2021, 3:26am UTC](https://vapor.discourse.group/t/failed-to-initialize-derived-coord-variable/112/9 "2021-08-31T03:26:33Z")
For some reason I always get some problems when I click on reply, the specific reply is above. Thanks for your help. ---
**Author:** ![clyne](https://avatars.discourse-cdn.com/v4/letter/c/b9e5f3/32.png) [@clyne](https://vapor.discourse.group/u/clyne)\ **Post date:** [August 31, 2021, 5:59pm UTC](https://vapor.discourse.group/t/failed-to-initialize-derived-coord-variable/112/10 "2021-08-31T17:59:51Z")
Thanks for providing the data set. I’ve opened an issue on GitHub here: > > > When attempting to flow render a data set provided by @yoghurt the flow renderer… fails with: > > \`\`\` > Error performing paint event > Update deltaT failed! > One of the selected volume dimension is zero! > \`\`\` > To reproduce: > 1. Load the data set /glade/p/cisl/vast/vapor/Bugs/\/uvw\_2016-06-23\_07\_20\_24.nc > 2. Enable the flow renderer We will get this addressed as soon as we can. You can check progress or provide additional information at the link above. ---
**Author:** ![clyne](https://avatars.discourse-cdn.com/v4/letter/c/b9e5f3/32.png) [@clyne](https://vapor.discourse.group/u/clyne)\ **Post date:** [September 22, 2021, 10:51pm UTC](https://vapor.discourse.group/t/failed-to-initialize-derived-coord-variable/112/11 "2021-09-22T22:51:38Z")
FYI there has been an update to your issue opened here: [VAPOR doesn't support 1D coordinate variables that are monotonically decreasing · Issue #2848 · NCAR/VAPOR · GitHub](https://github.com/NCAR/VAPOR/issues/2848)