real time plotting

[Xaego]

Could you help me make real time plotting with H2O wave?
I can do it static, but how to make it realtime?

import time

import numpy as np
import pandas as pd
from h2o_wave import site, ui, data, app, Q


def gen_random_array():
    num_rows = 3000
    df = pd.DataFrame(dict(
        pix=range(num_rows),
        intensity=np.random.random(num_rows)
    ))
    return df

df = gen_random_array()

page = site["/random_monitor"]

plot_1 = page.add("plot_intensity(pix)", ui.plot_card(
    box="1 1 6 4",
    title="Line",
    data=data(
        # fields=df.columns.tolist(),
        # rows=df.values.tolist(),
        fields="={{df.columns.tolist()}}",
        rows=dict(pix=df["pix"], intensity=df["intensity"]),
    ),
    plot=ui.plot(marks=[ui.mark(
        type='line',
        x='=pix', x_title='Length',
        y='=intensity', y_title='Width', shape='circle',
    )]
    )
))

while True:
    df = gen_random_array()
    plot_1.data.usage = df

    pix = df["pix"]
    intensity = df["intensity"]

    plot_1.data.pix = pix
    plot_1.data.intensity = intensity
    plot_1.plot_data[-1] = [pix, intensity]

    page.save()
    time.sleep(1)

[mturoci]

Hi @Xaego.

Unfortunately, your code is throwing an error for me:

Traceback (most recent call last):
  File "/Users/martinturoci/go/src/github.com/h2oai/telesync/py/examples/hello_world.py", line 37, in <module>
    page.save()
  File "/Users/martinturoci/go/src/github.com/h2oai/telesync/py/h2o_wave/h2o_wave/core.py", line 607, in save
    p = self._diff()
        ^^^^^^^^^^^^
  File "/Users/martinturoci/go/src/github.com/h2oai/telesync/py/h2o_wave/h2o_wave/core.py", line 552, in _diff
    d = marshal(dict(d=self._changes))
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/martinturoci/go/src/github.com/h2oai/telesync/py/h2o_wave/h2o_wave/core.py", line 1138, in marshal
    return json.dumps(d, allow_nan=False, separators=(',', ':'))
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/martinturoci/.asdf/installs/python/3.11.3/lib/python3.11/json/__init__.py", line 238, in dumps
    **kw).encode(obj)
          ^^^^^^^^^^^
  File "/Users/martinturoci/.asdf/installs/python/3.11.3/lib/python3.11/json/encoder.py", line 200, in encode
    chunks = self.iterencode(o, _one_shot=True)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/martinturoci/.asdf/installs/python/3.11.3/lib/python3.11/json/encoder.py", line 258, in iterencode
    return _iterencode(o, 0)
           ^^^^^^^^^^^^^^^^^
  File "/Users/martinturoci/.asdf/installs/python/3.11.3/lib/python3.11/json/encoder.py", line 180, in default
    raise TypeError(f'Object of type {o.__class__.__name__} '
TypeError: Object of type Series is not JSON serializable

So I would focus on fixing it first.

Apart from that, I suggest having a look at https://wave.h2o.ai/docs/buffers/ to understand how Wave data buffers work. Your code currently uses fixed buffer. However, for realtime updates, you most likely want to use cyclic buffer (FIFO) instead so that all you need to do is append new data and drop the old one.

You will need plot_1.plot_data[-1] = [pix, intensity] once cyclic_buffer is configured. However, both pix and intensity need to be primitive values as the line corresponds to a single tabular row within the dataset.

[Xaego]

Hi @mturoci
thank you. I still fight with it.

could you clarify if its possible to make program which I needed with H2o wave?
because I tried different dashboard lib and after 2 week understand its impossible...

I need program which is can:
0 work on local relative weak pc without network. like Lenovo ThinkCentre M700 Tiny
1 take real time 2d data from device.
2 plot it each 0.3-0.5 sec. subplot_1
3 have subplot_2 for sum all values of plot from 1 vs iteration. also real time
4 have button which stop current measurement and send commands to arduino and my sensor.
5 can still make realtime plots after step 4
6 have button for closing connection to arduino and my sensor

[mturoci]

Yes, totally possible. However, if you want to also handle user interactions (button clicks), you will need to use apps, not scripts.

Based on what you describe it seems like what you want is a background job that reads the data from arduino and plots them and then a simple UI for controlling the arduino around that. Have a look at https://medium.com/@unusualcode/background-jobs-in-wave-or-how-not-to-kill-your-ui-ae1fed95693a to learn more about how to start background jobs, update Wave UI and stop them.