ValueError: x and y must have same first dimension, but have shapes (11,) and (15406,

[hobbyist]

Ok, so I have an excel with 15000 measurements, (1st column:timestamps, 2nd column values). I want to represent them to a plot, where on the y-axis will be the measurements (the graph) and on the x-axis totally 20-25 values. I cannot obviously put 15000 xticks. I follow this code:

import datetime as dt
import numpy as np
import matplotlib.pyplot as plt
import matplotlib.dates as mdates

time = mdates.drange(dt.datetime(2014, 12, 20), dt.datetime(2015, 1, 2),
                     dt.timedelta(hours=2))
y = np.random.normal(0, 1, time.size).cumsum()
y -= y.min()

fig, ax = plt.subplots(figsize=(8, 6))
ax.plot(time, y, 'bo-')
ax.set(title='Active Calls', ylabel='Calls', xlabel='Time')
ax.grid()

ax.xaxis_date() # Default date formatter
fig.autofmt_xdate()

plt.show()

and I try to do modifications to the code in order to make it work...but I got errors like the one above. Can you help me?