kernel_lowpass has arguments when being called in Expwin source code, what value for x is being passed?

[shreyashi2104]

Taken from expwin.py in pygsp:

`def kernel_lowpass(x):
return h(0.5 - x/G.lmax + band_max)
def kernel_highpass(x):
return h(0.5 + x/G.lmax - band_min)

    if (band_min is None) and (band_max is None):
        kernel = lambda x: np.ones_like(x)
    elif band_min is None:
        kernel = kernel_lowpass  #Here what value of x is being passed
    elif band_max is None:
        kernel = kernel_highpass  #Here what value of x is being passed
    else:
        kernel = lambda x: kernel_lowpass(x) * kernel_highpass(x)`

This doubt came to my mind when I wanted to use expwin as high pass filter for my graph. Is this a glitch?

[nperraud]

I am not sure I understand your concern. I just tested expwin and everything seems alright.

import numpy as np
from pygsp.filters import Expwin
from pygsp.graphs import Sensor
from matplotlib import pyplot as plt

N = 100
slope = 4
G = Sensor(N)
G.estimate_lmax()
f1 = filters.expwin.Expwin(G, band_min=None, band_max=0.4, slope=slope)
f2 = filters.expwin.Expwin(G, band_min=0.2, band_max=None, slope=slope)
f3 = filters.expwin.Expwin(G, band_min=0.2, band_max=0.4, slope=slope)
plt.figure(figsize=(15,4))
ax = plt.subplot(131)
f1.plot(ax=ax);
ax = plt.subplot(132)
f2.plot(ax=ax);
ax = plt.subplot(133)
f3.plot(ax=ax);

Please precise your concern.

[shreyashi2104]

I wanted to know from the source code how kernel_lowpass is being called without arguments in case of band max or band min being None

…

On Wed, May 1, 2019, 1:19 PM nperraud ***@***.***> wrote: I am not sure I understand your concern. I just tested expwin and everything seems alright. import numpy as np from pygsp.filters import Expwin from pygsp.graphs import Sensor from matplotlib import pyplot as plt N = 100 slope = 4 G = Sensor(N) G.estimate_lmax() f1 = filters.expwin.Expwin(G, band_min=None, band_max=0.4, slope=slope) f2 = filters.expwin.Expwin(G, band_min=0.2, band_max=None, slope=slope) f3 = filters.expwin.Expwin(G, band_min=0.2, band_max=0.4, slope=slope) plt.figure(figsize=(15,4)) ax = plt.subplot(131) f1.plot(ax=ax); ax = plt.subplot(132) f2.plot(ax=ax); ax = plt.subplot(133) f3.plot(ax=ax); — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#49 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AHMSIMFYI54XDKX2CD2WANDPTFDSJANCNFSM4HJK2RXQ> .

[nperraud]

The function kernel_low pass is defined above taking the argument into account. I am closing the issue since this is not pygsp related.