how to plot time on y-axis in '%H:%M' format in matplotlib?

Question

i would like to plot the times from a datetime64 series, where the y-axis is formatted as \'%H:%M, showing only 00:00, 01:00, 02:00, etc.

this is what the plot look

Answer 1

For that to work you need to pass datetime objects (and I mean datetime, not datetime64). You can convert all timestamps to the same date and then use .tolist() to get the actual datetime objects.

y = df['a'].apply(lambda x: x.replace(year=1967, month=6, day=25)).tolist()
ax = plt.subplot()
ax.plot(df.index, y)
ax.yaxis.set_major_locator(HourLocator())
ax.yaxis.set_major_formatter(DateFormatter('%H:%M'))

Answer 2

You can try two things: 1) It should be ax.xaxis.... not ax.yaxis.... 2) Use set_major_locator() instead of set_major_formatter() for Locator. Example is shown below.

min = 15
ax.xaxis.set_major_locator(MinuteLocator(byminute=range(0,60,min)) )
ax.xaxis.set_major_formatter( DateFormatter('%H:%M') )