Remove the microseconds from matplotlib spectrogram

Question

I've been trying to plot an spectogram based on a wav file of 15 minutes lenght. I think I managed to do this, but I can't remove the microseconds from my x axis ( time axis). Any help with this, please?

This is the spectrogram obtained:

This is my code:

import matplotlib.pyplot as plt
import scipy.io.wavfile as wavfile
import matplotlib.ticker as ticker
from matplotlib.dates import DateFormatter, MinuteLocator
import time 
# Prettify
import matplotlib
import datetime
matplotlib.rc('figure', figsize=(17, 5))

cmap = plt.get_cmap('plasma') # this may fail on older versions of matplotlib
vmin = -40  # hide anything below -40 dB
cmap.set_under(color='k', alpha=None)

rate, frames = wavfile.read("audio_test.wav")
fig, ax = plt.subplots()
pxx, freq, t, cax = ax.specgram(frames[:, 0], # first channel
                                Fs=rate,      # to get frequency axis in Hz
                                cmap=cmap, vmin=vmin)
cbar = fig.colorbar(cax)
cbar.set_label('Intensity dB')
ax.axis("tight")



ax.set_xlabel('time h:mm:ss')
ax.set_ylabel('frequency kHz')

scale = 1e3                     # KHz
ticks = matplotlib.ticker.FuncFormatter(lambda x, pos: '{0:g}'.format(x/scale))
ax.yaxis.set_major_formatter(ticks)

def timeTicks(x, pos):
    d = datetime.timedelta(seconds=x)
    return str(d)
#formatter = matplotlib.ticker.FuncFormatter(timeTicks)
#ax.xaxis.set_major_formatter(formatter)

majorFormatter = matplotlib.dates.DateFormatter('%H:%M:%S') 
ax.xaxis.set_major_formatter(majorFormatter)
ax.xaxis.set_major_locator(ticker.IndexLocator(base=120, offset=60))
#ax.text(0.0, 0.1, "IndexLocator(base=0.5, offset=0.25)",
#        fontsize=14, transform=ax.transAxes)
plt.show()

Hello @Joe! Not quite. It's a ".wav" file with different audio sounds. But I'm not allowed to share it :( — PyRar
– PyRar, Commented Nov 23, 2018 at 8:10
You can try with something like this: majorFormatter = matplotlib.dates.DateFormatter('%H:%M:%S') ax.xaxis.set_major_formatter(majorFormatter) — Joe
– Joe, Commented Nov 23, 2018 at 8:14
Thank you @Joe ! It kind of works. But it shows me only "00:02:05" on the time axis. I'll update the photo of the spectrogram and the code. Don't know why it does this... — PyRar
– PyRar, Commented Nov 23, 2018 at 8:59
@Joe it return an error: TypeError: 'datetime.timedelta' object is not subscriptable — PyRar
– PyRar, Commented Nov 23, 2018 at 9:37

Joe · Accepted Answer · 2018-11-23 10:48:20Z

1

Using the code before your edit, you can change the return of def timeTicks(x, pos) in:

return str(d)[:7]

answered Nov 23, 2018 at 10:48

Joe

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