# Number of data viewer items shown

**URL:** <https://community.thunkable.com/t/number-of-data-viewer-items-shown/1462496>\
**Category:** Questions about Thunkable X\
**Tags:** beginner\
**Created:** [August 21, 2021, 11:31pm UTC](https://community.thunkable.com/t/number-of-data-viewer-items-shown/1462496 "2021-08-21T23:31:37Z")\
**Posts on this page:** 1\
**Showing post:** 2

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**Author:** ![tatiang](https://sea1.discourse-cdn.com/flex015/user_avatar/community.thunkable.com/tatiang/32/55482_2.png) [@tatiang](https://community.thunkable.com/u/tatiang)\
**Post date:** [August 22, 2021, 12:15am UTC](https://community.thunkable.com/t/number-of-data-viewer-items-shown/1462496/2 "2021-08-22T00:15:33Z")

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When you determine the three closest locations, you’ll need to modify your data source by deleting all of the rows and then creating three new rows for that information and then refreshing the data source.

Finding the three closest locations is not a simple matter. I’ve done this using the Haversine formula:

> [@Calculate distance travelled](https://community.thunkable.com/t/calculate-distance-travelled/565278):
>
> hello, its me again. how does one calculate distance travelled over time on a map in thunkable x? I intend on generating a notification if a certain distance is covered within x amount of time

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