I am trying to compute the modified z-score for anomaly detection purposes. When I try and take the median to compute the MAD (as shown in the image), I get the error

expected stream[A] but found (<-: stream[B]) => stream[{C with abs: D}] (function)

I am unsure of how to solve this error since median is working perfectly fine in `median`

. It is failing on line 19, where we take the median of `abs`

.

```
import "math"
data = from(bucket: "timeseries")
|> range(start: v.timeRangeStart, stop: v.timeRangeStop)
|> filter(fn: (r) => r["device"] == "XXXXXXXX")
|> keep(columns: ["_time", "_value", "_field"])
median = data
|> median()
|> map(fn: (r) => ({ r with median: r._value }))
|> keep(columns: ["median", "_field"])
abs = join(tables: {data: data, median: median}, on: ["_field"])
|> map(fn: (r) => ({ r with abs: math.abs(x: r._value - r.median) }))
|> keep(columns: ["_field", "abs"])
mad = abs
|> median() // CODE FAILS HERE: expected stream[A] but found (<-: stream[B]) => stream[{C with abs: D}] (function)
|> map(fn: (r) => ({ r with mad: r.abs }))
|> keep(columns: ["mad", "_field"])
modifiedZScore = join(tables: {data: data, mad: mad}, on: ["_field"])
|> map(fn: (r) => ({ r with modified_z_score: 0.6745 * (r._value - r.median) / r.mad }))
|> keep(columns: ["_time", "_value", "_field", "modified_z_score"])
|> yield()
```

Any help is greatly appreciated.