{{% note %}} This example uses [NOAA water sample data](/influxdb/version/reference/sample-data/#noaa-water-sample-data). {{% /note %}} This example compares the value from the latest point to an average value stored in another bucket. This is useful when using the average value to calculate a [threshold check](/influxdb/version/monitor-alert/checks/create/#threshold-check). The following query: - Uses [`range()`](/flux/v0/stdlib/universe/range/) to define a time range. - Gets the last value in the `means` bucket and compares it to the last value in the `noaa` bucket using [`last()`](/flux/v0/stdlib/universe/last/). - Uses [`join()`](/flux/v0/stdlib/universe/join/) to combine the results - Uses [`map()`](/flux/v0/stdlib/universe/map/) to calculate the differences ```js means = from(bucket: "weekly_means") |> range(start: 2019-09-01T00:00:00Z) |> last() |> keep(columns: ["_value", "location"]) latest = from(bucket: "noaa") |> range(start: 2019-09-01T00:00:00Z) |> filter(fn: (r) => r._measurement == "average_temperature") |> last() |> keep(columns: ["_value", "location"]) join(tables: {mean: means, reading: latest}, on: ["location"]) |> map(fn: (r) => ({r with deviation: r._value_reading - r._value_mean})) ``` ### Example results | location | _value_mean | _value_reading | deviation | |:-------- | -----------: | --------------:| ---------: | | coyote_creek | 79.82710622710623 | 89 | 9.172893772893772 | | santa_monica | 80.20451339915374 | 85 | 4.79548660084626 |