# FK beam forming: attribute error

**URL:** https://discourse.obspy.org/t/fk-beam-forming-attribute-error/1962
**Category:** Usage Questions
**Created:** [June 12, 2024, 11:31pm UTC](https://discourse.obspy.org/t/fk-beam-forming-attribute-error/1962 "2024-06-12T23:31:46Z")
**Posts on this page:** 3
**Page:** 1

<div class="post-metadata">

### Author: ![benjaminfernando](https://discourse.obspy.org/user_avatar/discourse.obspy.org/benjaminfernando/32/837_2.png) [@benjaminfernando](https://discourse.obspy.org/u/benjaminfernando)
#### Post date: [June 12, 2024, 11:31pm UTC](https://discourse.obspy.org/t/fk-beam-forming-attribute-error/1962/1 "2024-06-12T23:31:46Z")

</div>

Hi!

I’m getting an error I don’t really understand when following the “Beamforming: FK Analysis” guide.

MWE (copied parameters into a dictionary to make it easier to read):

```
lat_dict = {1: 39.49957, 2: 39.49991, 3: 39.50027, 4: 39.5006, 5: 39.4979, 6: 39.50036, 7: 39.50117, 8: 39.49919, 9: 39.49883, 10: 39.49844, 11: 39.49874}

```

long\_dict = {1: -116.50945, 2: -116.50838, 3: -116.50731, 4: -116.50623, 5: -116.50855, 6: -116.50994, 7: -116.51045, 8: -116.51052, 9: -116.51157, 10: -116.51262, 11: -116.5092}

elev\_dict = {1: 1917, 2: 1917, 3: 1919, 4: 1920, 5: 1921, 6: 1915, 7: 1912, 8: 1921, 9: 1915, 10: 1914, 11: 1920}

```
stream = obspy.read('array_data/MINISEED/combinedvertical.mseed') #contains 12 traces, all vertical

for i in range(1,11): 
    stream[i].stats.paz = AttribDict({'poles': [(-21.9911+22.4355j), (-21.9911-22.4355j)], 'zeros': [0j, 0j], 'gain': 76})
    stream[i].stats.coordinates = AttribDict({'latitude':lat_dict[i], 'elevation':elev_dict[i], 'longitude':long_dict[i]})

    # Execute array_processing
kwargs = dict(
    # slowness grid: X min, X max, Y min, Y max, Slow Step
    sll_x=-3.0, slm_x=3.0, sll_y=-3.0, slm_y=3.0, sl_s=0.03,
    # sliding window properties
    win_len=1.0, win_frac=0.05,
    # frequency properties
    frqlow=1.0, frqhigh=8.0, prewhiten=0,
    # restrict output
    semb_thres=-1e9, vel_thres=-1e9,
    stime=t1,
    etime=t2
)
out = array_processing(stream, **kwargs)

```

```python
returns the following error: 

  Cell In[99], line 1
    beamforming()

  File ~/Library/Mobile Documents/com~apple~CloudDocs/Work/Missions/ORX/array_analysis.py:101 in beamforming
    out = array_processing(stream, **kwargs)

  File ~/mambaforge/envs/cartopy-dev/lib/python3.12/site-packages/obspy/signal/array_analysis.py:917 in array_processing
    geometry = get_geometry(stream, coordsys=coordsys, verbose=verbose)

  File ~/mambaforge/envs/cartopy-dev/lib/python3.12/site-packages/obspy/signal/array_analysis.py:632 in get_geometry
    geometry[i, 0] = tr.stats.coordinates.longitude

  File ~/mambaforge/envs/cartopy-dev/lib/python3.12/site-packages/obspy/core/util/attribdict.py:142 in __getattr__
    raise AttributeError(e.args[0])

AttributeError: coordinates

```

---

<div class="post-metadata">

### Author: ![megies](https://discourse.obspy.org/user_avatar/discourse.obspy.org/megies/32/9_2.png) [@megies](https://discourse.obspy.org/u/megies)
#### Post date: [June 13, 2024, 9:31am UTC](https://discourse.obspy.org/t/fk-beam-forming-attribute-error/1962/2 "2024-06-13T09:31:59Z")

</div>

`range()` stop value is not used in the loop, the for loop uses `10` as its last vlaue, the last entry from your dictionaries is never assigned. I totally recommend not using `range()` in for loops. You’re much better of with for loops vaguely like `for item in iterable:` or using `enumerate()`:

```python
for i, tr in enumerate(st):
    tr.stats.coordinates = ... lat_dict[i] ...

```

In this case, I would totally recommend to just use a list and not a dictionary, to be honest, since the “mapping” concept is not really a mapping but just enumerated indices and then the for loop can be written much nicer with `zip()` which also avoids confusion with indices (mixing ‘1’ as first index in combination with Python having ‘0’ as first index is asking for trouble..).

```python
longs = [-116.50945, -116.50838, -116.50731, ...]

for tr, long, lat, elev in zip(st, longs, lats, elevs):
    tr.stats.coordinates = {'latitude': lat, ...}

```

---

<div class="post-metadata">

### Author: ![benjaminfernando](https://discourse.obspy.org/user_avatar/discourse.obspy.org/benjaminfernando/32/837_2.png) [@benjaminfernando](https://discourse.obspy.org/u/benjaminfernando)
#### Post date: [June 20, 2024, 3:10pm UTC](https://discourse.obspy.org/t/fk-beam-forming-attribute-error/1962/3 "2024-06-20T15:10:01Z")

</div>

Thanks! Stupid move on my part.

A follow-up: does this beamforming routine at some level implicitly assume a source below the stations? I am looking at a source in the atmosphere and the peak in the BAZ is 180 degrees out from what I expect.